Somewhat minor, but which could be a bit less ambiguous.
When the "Replace only in category" filter is used. And Replace-Text can't find the target string in any of the pages listed in the targeted category. It comes back with: No category exists with the name "Category:<+name>".
Technically:
1) Replace-Text just could not find any page that matched the search string.
2) Categories are of course a bit tricky. As they can exist as a page, but still be empty. Or they can contain pages, without actually having some page-content set.
Something like No matching pages found in/for the "Category:<+name>" seem a better feedback text for these cases.
Replace Text: 1.7 (8e35c8f) 19:50, 4 December 2022 MediaWiki: 1.39.0