I have the following tikzcd diagram, where I am trying to create an a line between the nodes B and A/I.
I tried using two phantom nodes and join an arrow between them, but nothing shows up except a dot where the arrow is supposed to be.
(Also, the thickness of the line adjoining C and I is thicker than C/I to 0 for some reason)
\documentclass{article}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}[column sep=0em,row sep=1em]
&R\arrow[dl,dash]\arrow[dr,dash] &&&&& R/I\arrow[dl,dash]\arrow[dr,dash]\\
A\arrow[dr,dash] && B\arrow[dl,dash] &\phantom{X}\arrow[r,dash]&\phantom{Y}& A/I\arrow[dr,dash] && B/I\arrow[dl,dash]\\
&C\arrow[d,dash] &&&&& C/I\arrow[d,dash]\\
&I &&&&& 0
\end{tikzcd}
\end{document}