Since a few days ago (probably¹ 1.26wmf6?), added_lines starts with a white space which is not present in the new wikitext of the page.
For example, on
mw.config.get('wgAbuseFilterVariables')['added_lines'] === " "
returns true (in the JS console), but I didn't add any space before the "#" when I attempted to make that edit. Compare the values of new_wikitext and added_lines.
Due to this regression, filters such as
started to have many false positives, warning users incorrectly.
There might be others filters broken out there, whose maintainers simply didn't notice (yet).
¹ This seems to be the first log with the problem on Portuguese Wikipedia: