Your comments

Weird. Wonder why it's Cmd-Y on mine.
I also suggest using the key commands cmd-[ and cmd-] to mean back and forward, to respect web browsers on the Mac. I have my mouse's back and forward buttons bound to those keystrokes.
Why not just hit paste twice? Or use the duplicate command if that's what you want. Doesn't seem logical to build in special cases to the paste command that change its behavior when it's more valuable to behave consistently with other apps, imo.
This is one of my favorite code editor features! I really miss it when it's not there.
On the other hand, it can still be useful to find paired brackets within large blocks of commented code.

So really, it should depend on whether the selected bracket is commented or not as to whether the matched bracket should also be commented or not.