Can anyone explain why setting \lineskiplimit breaks align?

Question

OK, so this is a follow-up to one of my previous questions:

If you uncomment the \lineskiplimit line, LaTeX goes crazy. Why? Does anyone have an idea how to fix it (without manually changing \lineskiplimit temporarily, or hacking into amsmath, which seems a bit nightmare-ish)?

\documentclass{article}

%\lineskiplimit=-\maxdimen
\usepackage{amsmath}

\begin{document}
A sample aligned equation:
\begin{align*}
  c^2&=a^2+b^2
\end{align*}
\end{document}

Answer 1

Here you find one of the reasons: amsmath.sty says

\def\@display@init#1{%
    \global\dt@ptrue \spread@equation
    \everycr{%
        \noalign{%
            #1%
            \ifdt@p
                \global\dt@pfalse
                \vskip-\lineskiplimit
                \vskip\normallineskiplimit
            \else
                \penalty\@eqpen \global\dspbrk@lvl\m@ne
            \fi
        }%
    }%
}

and this of course has quite a bizarre consequence:

Overfull \vbox (15864.60002pt too high) has occurred while \output is active

It's not a good idea to set \lineskiplimit=-\maxdimen except in very controlled situations such as tabulars where struts can be inserted (and are, actually).