Hiding the mouse cursor does makes sense in a lot of situations I agree, but it's very much a preference thing, and I don't see a good reason to change the original behavour. Some people (i.e. me) don't like cursors disappearing in windowed mode when you move the cursor over the screen, but most importantly, it makes the editor much less pleasant to use (since you're relying on the 30fps editor cursor box).
I'd be happy to support, say, a setting that allowed you to disable the mouse cursor, or even a 15 second time-out which makes the cursor disappear if not moved (and reappear once moved), but just having it off by default feels wrong to me.
This disables being able to press M to mute while editing a script in
the script editor. It also disables it in the script list, too, but I'm
hoping no one thinks that's an issue, because I personally don't think
it is.