It seems that Discuss.Online keeps archival copies of such older messages rather than delete them after a defederation action. Try viewing them on that instance.

On a separate matter, this is a brand-new message that for that and perhaps other reasons I doubt you've seen but that you may be very interested to know about: https://lemmygrad.ml/post/6127949/5423163. The post itself is talking about the upcoming defederation between jlai.lu and lemmygrad.ml, which I'm sure you know about, but what I wanted to call your attention to is in the OP's comment where they immediately start talking about a method to use a 2nd account or some other method to bypass that defederation attempt. They also float an idea to change the Lemmy sourcecode so that admins can no longer control which instances their users can access - this seems like an enormous security issue to me though (e.g. CSAM and other outright violent rhetoric that could get someone in trouble if it were on their machines).

Anyway no matter how you slice it, it is uh... "interesting". The more of such discussions I see, the more glad I am that I switched to PieFed that does not depend upon the Lemmy sourcecode at all - even though Discuss.Online was great.