Using booktabs and \tabular I get a heavy vertical rule on the right edge only

Question

My table is filled and all boxes are filled. I have made similar tables elsewhere in the document with no issues. (It is a conjugation table for verbs in a conlang I'm making, if you're wondering.)

My table:

\documentclass[12pt, a4paper, draft]{report}
\usepackage{multirow, booktabs} % table packages
\usepackage{graphicx}
\begin{document}
\begin{tabular}{llcccc}
    \toprule
    \textbf{ASPECT} &\textbf{MOOD} &\textbf{A-CLASS} &\textbf{O-CLASS} &\textbf{U-CLASS} &\textbf{I-CLASS} \cr
    \midrule
    \multirow{8}{*}{\textbf{\rotatebox{90}{CONTINUOUS}}} &\textbf{INDICATIVE} &JAL &JOL &JUL &JIL
    \\ &\textbf{SUBJUNCTIVE} &JATAL &JOTOL &JUTUL &JITIL
    \\ &\textbf{OPTATIVE} &JAJA &JOJO &JUJU &JIJI
    \\ &\textbf{IMPERATIVE} &JATAI &JOTOI &JUTE &JITĪ
    \\ &\textbf{JUSSIVE} &JAJAI &JOJOI &JEJU &JIJIA
    \\ &\textbf{INTERROGATIVE} &JANA &JONŌ &JUNŪ &JINĪ
    \\ &\textbf{CONDITIONAL} &JAKA &JOKO &JUKU &JILKI
    \\ &\textbf{CONATIVE} &JAVAL &JOVOL &JUVĒIL &JIVIL 
    \\ &\textbf{JOCATIVE} &JAM &JŌM &JŪM &JĪM
    \\ &\textbf{SARCASTATIVE} &JAN &JON &JŪN &JĪN \cr
    \midrule
    \multirow{8}{*}{\textbf{\rotatebox{90}{PERFECTIVE}}} &\textbf{INDICATIVE} &FĀL &FOL &FEL &LILF
    \\ &\textbf{SUBJUNCTIVE} &FATAL &FOTŌL &FUTEL &FIL
    \\ &\textbf{OPTATIVE} &FĀI &FŌI &FĒ &FĪJĪ
    \\ &\textbf{IMPERATIVE} &FATI &FOTI &FUTI &FI
    \\ &\textbf{JUSSIVE} &FAJI &FOJI &FUJI &FIJ
    \\ &\textbf{INTERROGATIVE} &FANA &FONO &FUNI &FINĪ
    \\ &\textbf{CONDITIONAL} &FĀKA &FŌKO &FŪKŪ &FĪV
    \\ &\textbf{CONATIVE} &FĀVA &FŌVO &FŪVO &FĪV
    \\ &\textbf{JOCATIVE} &FAM &FŌM &FŪM &FĪM
    \\ &\textbf{SARCASTATIVE} &FAN &FON &FŪN &FĪN \cr
    \bottomrule
\end{tabular}
\end{document}

Answer 1

As @JohnKormylo has already noted in a comment, LaTeX inserts a thick vertical line -- knows as a "slug" in typography jargon -- along the right-hand edge of the tabular environment because (a) the draft document class option has been set and (b) the width of the tabular environment exceeds the value of \textwidth.

Short of rewriting and simplifying the entire table, the best way to get make the material in the available space is to simplify the headers of the four data columns. Below is a suggested solution which puts the word "class" across all four data columns.

\documentclass[12pt, a4paper, draft]{report}
\usepackage{multirow, booktabs, graphicx}
\begin{document}
\begin{center}
\begin{tabular}{@{}llcccc@{}}
    \toprule
    \textbf{ASPECT} &\textbf{MOOD} 
    &\multicolumn{4}{c@{}}{\textbf{CLASS}}\\
    \cmidrule(l){3-6}
    &&\textbf{A} &\textbf{O} &\textbf{U} &\textbf{I} 
    \\ \midrule
    \multirow{8}{*}{\textbf{\rotatebox{90}{CONTINUOUS}}} 
       &\textbf{INDICATIVE}   &JAL   &JOL &JUL &JIL
    \\ &\textbf{SUBJUNCTIVE}  &JATAL &JOTOL &JUTUL &JITIL
    \\ &\textbf{OPTATIVE}     &JAJA  &JOJO &JUJU &JIJI
    \\ &\textbf{IMPERATIVE}   &JATAI &JOTOI &JUTE &JITĪ
    \\ &\textbf{JUSSIVE}      &JAJAI &JOJOI &JEJU &JIJIA
    \\ &\textbf{INTERROGATIVE}&JANA  &JONŌ &JUNŪ &JINĪ
    \\ &\textbf{CONDITIONAL}  &JAKA  &JOKO &JUKU &JILKI
    \\ &\textbf{CONATIVE}     &JAVAL &JOVOL &JUVĒIL &JIVIL 
    \\ &\textbf{JOCATIVE}     &JAM   &JŌM &JŪM &JĪM
    \\ &\textbf{SARCASTATIVE} &JAN   &JON &JŪN &JĪN 
    \\ \midrule
    \multirow{8}{*}{\textbf{\rotatebox{90}{PERFECTIVE}}} 
       &\textbf{INDICATIVE}   &FĀL   &FOL &FEL &LILF
    \\ &\textbf{SUBJUNCTIVE}  &FATAL &FOTŌL &FUTEL &FIL
    \\ &\textbf{OPTATIVE}     &FĀI   &FŌI &FĒ &FĪJĪ
    \\ &\textbf{IMPERATIVE}   &FATI  &FOTI &FUTI &FI
    \\ &\textbf{JUSSIVE}      &FAJI  &FOJI &FUJI &FIJ
    \\ &\textbf{INTERROGATIVE}&FANA  &FONO &FUNI &FINĪ
    \\ &\textbf{CONDITIONAL}  &FĀKA  &FŌKO &FŪKŪ &FĪV
    \\ &\textbf{CONATIVE}     &FĀVA  &FŌVO &FŪVO &FĪV
    \\ &\textbf{JOCATIVE}     &FAM   &FŌM &FŪM &FĪM
    \\ &\textbf{SARCASTATIVE} &FAN   &FON &FŪN &FĪN 
    \\ \bottomrule
\end{tabular}
\end{center}
\end{document}

Answer 2

I would redesign your table, similarly as @Mico did in his nice answer (+1). With use of the packages rotating and makecell beside already used, the suggested MWE is:

\documentclass[12pt, a4paper, draft]{report}
\usepackage{rotating}
\usepackage{booktabs, makecell, multirow}
\renewcommand\theadfont{\normalsize\bfseries}
\renewcommand\theadgape{}
%---------------- show page layout. don't use in a real document!
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%

\begin{document}
\begin{center}
\setlength\tabcolsep{0pt}
\settowidth\rotheadsize{\theadfont  CONTINUOUS}
\begin{tabular*}{\linewidth}{@{\extracolsep{\fill}} >{\bfseries}c 
                                                    >{\bfseries}l *{4}{l}
                            }
    \toprule
\multirow{2.4}{*}{ASPECT}  
    &   \multirow{2.4}{*}{MOOD}
        &\multicolumn{4}{c@{}}{\thead{CLASSES}}\\
    \cmidrule(l){3-6}
    &   &   \thead{A} &\thead{O} &\thead{U} &\thead{I}  \\ 
    \midrule
\multirow{10}{*}{\rothead{CONTINUOUS}}
    &INDICATIVE    &JAL   &JOL   &JUL    &JIL   \\ 
    &SUBJUNCTIVE   &JATAL &JOTOL &JUTUL  &JITIL \\ 
    &OPTATIVE      &JAJA  &JOJO  &JUJU   &JIJI  \\ 
    &IMPERATIVE    &JATAI &JOTOI &JUTE   &JITĪ  \\ 
    &JUSSIVE       &JAJAI &JOJOI &JEJU   &JIJIA \\ 
    &INTERROGATIVE &JANA  &JONŌ  &JUNŪ   &JINĪ  \\ 
    &CONDITIONAL   &JAKA  &JOKO  &JUKU   &JILKI \\ 
    &CONATIVE      &JAVAL &JOVOL &JUVĒIL &JIVIL \\ 
    &JOCATIVE      &JAM   &JŌM   &JŪM    &JĪM   \\ 
    &SARCASTATIVE  &JAN   &JON   &JŪN    &JĪN   \\ 
    \midrule
\multirow{10}{*}{\rothead{PERFECTIVE}}
    &INDICATIVE    &FĀL   &FOL   &FEL    &LILF  \\ 
    &SUBJUNCTIVE   &FATAL &FOTŌL &FUTEL  &FIL   \\ 
    &OPTATIVE      &FĀI   &FŌI   &FĒ     &FĪJĪ  \\ 
    &IMPERATIVE    &FATI  &FOTI  &FUTI   &FI    \\ 
    &JUSSIVE       &FAJI  &FOJI  &FUJI   &FIJ   \\ 
    &INTERROGATIVE &FANA  &FONO  &FUNI   &FINĪ  \\ 
    &CONDITIONAL   &FĀKA  &FŌKO  &FŪKŪ   &FĪV   \\ 
    &CONATIVE      &FĀVA  &FŌVO  &FŪVO   &FĪV   \\ 
    &JOCATIVE      &FAM   &FŌM   &FŪM    &FĪM   \\ 
    &SARCASTATIVE  &FAN   &FON   &FŪN    &FĪN   \\ 
    \bottomrule
\end{tabular*}
\end{center}
\end{document}

(red lines indicate text borders)

Answer 3

Reducing the font size to \footnotesize allows to fit the table in the page:

\documentclass[12pt, a4paper, draft]{report}
\usepackage{multirow, booktabs} % table packages
\usepackage{graphicx}
\begin{document}
{
    \scriptsize % just reduce the font size
    \begin{tabular}{llcccc}
        \toprule
        \textbf{ASPECT} &\textbf{MOOD} &\textbf{A-CLASS} &\textbf{O-CLASS} &\textbf{U-CLASS} &\textbf{I-CLASS} \cr
        \midrule
        \multirow{8}{*}{\textbf{\rotatebox{90}{CONTINUOUS}}} &\textbf{INDICATIVE} &JAL &JOL &JUL &JIL
        \\ &\textbf{SUBJUNCTIVE} &JATAL &JOTOL &JUTUL &JITIL
        \\ &\textbf{OPTATIVE} &JAJA &JOJO &JUJU &JIJI
        \\ &\textbf{IMPERATIVE} &JATAI &JOTOI &JUTE &JITĪ
        \\ &\textbf{JUSSIVE} &JAJAI &JOJOI &JEJU &JIJIA
        \\ &\textbf{INTERROGATIVE} &JANA &JONŌ &JUNŪ &JINĪ
        \\ &\textbf{CONDITIONAL} &JAKA &JOKO &JUKU &JILKI
        \\ &\textbf{CONATIVE} &JAVAL &JOVOL &JUVĒIL &JIVIL
        \\ &\textbf{JOCATIVE} &JAM &JŌM &JŪM &JĪM
        \\ &\textbf{SARCASTATIVE} &JAN &JON &JŪN &JĪN \cr
        \midrule
        \multirow{8}{*}{\textbf{\rotatebox{90}{PERFECTIVE}}} &\textbf{INDICATIVE} &FĀL &FOL &FEL &LILF
        \\ &\textbf{SUBJUNCTIVE} &FATAL &FOTŌL &FUTEL &FIL
        \\ &\textbf{OPTATIVE} &FĀI &FŌI &FĒ &FĪJĪ
        \\ &\textbf{IMPERATIVE} &FATI &FOTI &FUTI &FI
        \\ &\textbf{JUSSIVE} &FAJI &FOJI &FUJI &FIJ
        \\ &\textbf{INTERROGATIVE} &FANA &FONO &FUNI &FINĪ
        \\ &\textbf{CONDITIONAL} &FĀKA &FŌKO &FŪKŪ &FĪV
        \\ &\textbf{CONATIVE} &FĀVA &FŌVO &FŪVO &FĪV
        \\ &\textbf{JOCATIVE} &FAM &FŌM &FŪM &FĪM
        \\ &\textbf{SARCASTATIVE} &FAN &FON &FŪN &FĪN \cr
        \bottomrule
    \end{tabular}
}
\end{document}