I guess it's time for a welcome then
We don't have any fancy welcomes like "...and sorry 'bout your wallet" (Head-Fi style), but I guess that one equally applies here
But on that matter of RShift, that's quite interesting actually. I honestly had to check when I use it, but it seems I do make use of it for a few keys on the very right, mostly non-character stuff (colon, semicolon, apostrophe, asterisk, accents, question mark).
The underscore is interesting, since for typing "RANDOM_CONSTANT" I'd use LShift (which is already in use anyway and keeps the left hand from moving around) but lowercase "some_file.ext" would make use of RShift (with the whole left hand moving over).
Another interesting part is that for some things on the right, like Ä, I make use of LShift while entering the letter with the right hand - makes sense though, as those letters would typically be followed up with others far more towards the left, so the left hand won't have to travel as far.
And yes, I'm a lefty with original IdiosyncraType[tm] technique (almost all left hand, right is mainly for nav keys, numblock and pointing rodent) and German layout.
For regular typing, I tend to use whichever Shift is closest in all-lefty operation, but almost always LShift when I'm also using the right hand (extending to O-K-M or so).