I've noticed this quite often too. Sometimes the I realize I need to enclose something in brackets after it's been typed, so I put the end bracket first since i'm already at the end, then go to the beginning, and magically that extraneous bracket appears. Ah well, it's clearly a very simple logic error that would take all of five seconds to fix, they just have to do it...
It's horrible. I filed 12022215 against that at the start of August 2012, closed as a dupe of 11339104. Still not fixed.
I've learned the muscle memory when I insert a paren like that to use the left arrow over it, then the right arrow and THEN type the space. That stops it happening but it should be fixed.
I wonder if the variable-completion bug in the debugger is fixed, the one where after a while it would autocomplete but not in 'ghost' mode, but in full type mode so you end up with garbage at the end of the line as you keep typing.
I filed that one last year too, they asked me to test the fix, I did, said it didn't work, and the bug was closed anyway which I found rather annoying.