Commenting is something built into a language.  As there aren't any comments in any of the entity files, the function was likely never added into their system.

You could do this as part of your develop/deploy process by developing a small process that strips lines that start with your preferred comment block and generates a clean entity file for testing in Sins. A little work on your part but if it's important to you it wouldn't be difficult to create.

I already prefer already to develop in a directory outside of the mod folder that is tied to a source code repository tool and then use ant to deploy to the various mod directories I maintain (one for unit testing, and one for shared alpha testing currently). If I want to see what I changed I can do compares against the history stored in the source repository so comments haven't been a priority for me but it has crossed my mind. I more miss comments for putting TODO blocks in the code so I can be reminded I wanted to come back to something later.

Check out code.google.com for maintaining source history and eclipse as a development platform.

This thread has some info on eclipse (https://forums.sinsofasolarempire.com/380774) and a entity validation tool I have written if your interested (I use subversion feature to do the source code control). Even for a small project I find performing checkins at various milestones a good habit to maintain. I created a project called zombiesrus5 on code.google.com just for little side projects. I have another one for a larger mod I am working on.