Does anybody use Rename Special | Batch Rename to change extensions?? I doubt it. Anyway, the dialog says "The original file extensions are preserved if the pattern contains no extension." This is true, but the common sense (logically incorrect but...)
inversion of it "Extensions are changed if the pattern contains an extension" is not true as I found out today by a coincidence. So the function is buggy.
Now I thought about it and came to the conclusion that the function should make a clearer statement about extensions (as the other rename functions already do!). And it should be:
"The original file extensions remain unchanged." Period. This allows you to enter patterns containing a dot without having to fear that you lose your extensions.
Okay?

I'm prepared for objections! If a voice
pro extension changing is raised, I will strike back with a
/e-switch!