Block mode selects don't know whether to wrap lines or not; most half-decent terminals keep track of whether wrapping was due to carriage return or hitting the last column.

I do this all the time to e.g. select deleted files from a git status command so I can xclip paste the selection out through awk to xargs git rm (or rather, use some scripts which simplify the above). Similarly for rspec / cucumber test results to extract out the failures for use with $(<failures.txt) on repeated runs as I fix broken tests. I have a script that analyzes ruby stack traces, which I copy from the crashed session. All sorts of ad-hoc clickery, I rely on word wrap being detected consistently.

wow, thank you for that. That just made my use of tmux that much easier!