I've never had a problem with this when moving code around. Cut/paste, indent entire block to match initial level, done. Where is the potential for errors? There really is none, because the brainbox keeps track of what I just pasted and tab/shift-tab moves that block as a unit. I find moving stuff around in braced languages a wee bit more work, actually, because you have to move the braces manually instead of shifting the block in and out, which is quicker.

Personally I've been way more annoyed when I've typed something up in the REPL and can't paste that over directly because of the >>> and ... but that's really a small tooling issue; a smarter editor would remove the REPL marks when pasting. Same for other REPL languages, most of them have PSn...