I know how to do it (although I'm slow at it), but it seems to me like I should be able to see the algorithm instantly without a viewpoint shift for every case in BH corners anyway, so I don't really see the point in practicing viewpoint shifting.
Yes I suppose that ideally you should be able to identify and see each case without viewpoint shifting. I view it as a compromise between efficiency and speed. Ideally I should be able to solve the Rubik's cube in sub-35 moves every time, however I find it to be faster to solve in 55 moves with less efficiency. I treat viewpoint shifting the same way. Sure I should be able to identify each case from the angle given, but I find it to be faster to just viewpoint shift the difficult cases.
Here is an example of a case that I
can recognize from the angle by itself, but even still I have a difficult time picturing the commutator. I find it to not only be faster, but much easier, to always viewpoint shift on this case:
UBL -> BUR -> FUL
When I see this case, especially when going quickly, I am tempted to think it's a Cyclic Shift, but it's actually an A9. If you viewpoint shift every sticker once clockwise you can see that it's:
LUB -> RBU -> LFU
which is easily done as: R B2 R F2 R' B2 R F2 R2
I am learning to recognize more cases from the actual angle without viewpoint shifting, and maybe it is a crutch that I should stop using, but I find it to speed up my recognition. Perhaps this is only the beginner version, and I should work up to identifying all cases from the original angle. I never thought about that.
--edit--
Then again, the only commutator I've been using consistently is A-perm but I don't even look at it in a commutator way.
To get used to seeing the A perm as a commutator try solving cycles like:
UBL -> BUR -> BRD
UBL -> BRD -> BUR
UBL -> FRU -> FDR
UBL -> FDR -> FRU
They are essentially variations on the A perm.
Chris