I can live with the delay and continue to patch my version locally. Thanks for sharing these details about scintilla/lexilla/test. Not sure what to do with this information though since I have no idea about the internal test infrastructure and do not use it either, sorry. This is just a bug report showing a minimal test case and offering a way to fix the issue, which works for me. :)
lex-latex: %\end{comment} inside \begin{comment} environment