I think it could slightly depend on the context. For example at the beginning of a sentence you'll have an upper case but not in the middle. Similarly there might be some occurrences of "error: %s" where it's better to have "error: out of memory" than "error: out of memory error". But I sincerely doubt we have that many different contexts and it's likely that 2 or 3 at most would be needed.

Yes, it's not a 100% mindless search and replace. I did look into a few places while writing up this issue: Most of them have exactly the same context (usually config parsing) and are worded slightly differently. Adjusting all the ones in the config parser and similar is a no brainer.