Ouch. You're right. I'll have to think that through some more before
implementing anything.
We actually have this problem already at the per-word level, but it's far
less pronounced than with a sentence-level replacement.
Any time we replace *anything* (from the find or spell dialogs) we can
potentially lose interior character-level formatting. However, people are
far less likely to have inter-word formatting changes, so they're unlikely
to notice that we nuke them.
But having the same behavior in a trivial sentence-level replacement is
bound to be more noticeable. At minimum, we should localize the edit
operations, which would help, but that's not a real solution.
As I said, this needs more thought.
Paul