DiscussionTools hides cite errors. I noticed this while debugging T301213 (and it made that bug more difficult to understand).
For example, see this page: https://test.wikipedia.org/w/index.php?title=Talk:Cite_error&action=edit
== test == hi [[User:Matma Rex|Matma Rex]] ([[User talk:Matma Rex|talk]]) 05:42, 16 February 2022 (UTC) :hello <ref>?<ref> [[User:Matma Rex|Matma Rex]] ([[User talk:Matma Rex|talk]]) 05:43, 16 February 2022 (UTC) ::hello <ref>?</ref> [[User:Matma Rex|Matma Rex]] ([[User talk:Matma Rex|talk]]) 05:43, 16 February 2022 (UTC)
The unclosed <ref> tag in the second comment causes the third comment not to be visible on the page (because all content up to the </ref> is replaced with an error).
With the reply tool enabled, there is no indication that anything is wrong:
https://test.wikipedia.org/wiki/Talk:Cite_error?dtenable=1:
With the reply tool disabled, there's a clear error message:
https://test.wikipedia.org/wiki/Talk:Cite_error?dtenable=0:
