In visual mode it actually behaves the way you want. I think we didn't do it for wikitext because we didn't want to get into wikitext parsing.

As a workaround, you can type ~~~~ yourself on a new line (on generally, wherever you want the signature to be), and the tool won't add an extra signature.

In T263217#6475606, @matmarex wrote:

In visual mode it actually behaves the way you want. I think we didn't do it for wikitext because we didn't want to get into wikitext parsing.

I still don't like adding more logic that depends on wikitext parsing, but maybe at this point this is worth making an exception.

Change 820839 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/DiscussionTools@master] Add signature on separate line if wikitext comment ends with a list

https://gerrit.wikimedia.org/r/820839

Change 820839 merged by jenkins-bot:

[mediawiki/extensions/DiscussionTools@master] Add signature on separate line if wikitext comment ends with a list

https://gerrit.wikimedia.org/r/820839

✅ Discussion tools places on a new line as expected