I'm  using Kile 2.1.3 (on Mint 18.3).

After everything else in my document (report class), I have the following code:

\begin{comment}
\appendix
\chapter*{Appendix}
\section*{Frobnicate the bar}
Bunch of text here, etc. etc.
\endcomment}

... and this shows up as part of the document structure tree, which it really shouldn't - especially seeing how the comment environment is identified and its contents is grayed-out.

This bug seems very related to bug 63121, which was about line comments (text after the % symbol). However, that one was resolved 15 years ago. In fact, if I add line comments within the comment environment, the appendix and the section disappear from the structure tree; so it really looks like they're treated like a normal part of the document.