Welcome to the ZDoom Forums!

Alright, fair enough. If you can figure out why the bullet tracer does not obey mirror rules, that would definitely be something ideal to be fixed.

My bad, apparently it does work as intended. I wrote this post cause I couldn't get this to work with a bullet tracer actor, but now I went and made a test map with some generic props and it seems to work fine.
Still have to figure out why it doesn't work specifically with this bullet tracer, but if there's anything quirky I'll make another thread, this can be closed.

I agree with Gez, and I'm surprised that hasn't been implemented already, seems like an oversight. When you have some spare time please provide a demo wad with both plane and wall mirrors and I will see about getting this done.

IMO it should be the same flag; there's no real reason for separating the surfaces here.

As the title says, I noticed +INVISIBLEINMIRRORS doesn't work on reflective floors and ceilings, would a hypothetical +INVISIBLEONPLANES flag be possible? I think it would be very useful for various things (map performance optimization, full "vampire" characters that don't reflect their image anywhere etc)