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I think discussion duration is a big factor. For sites like HN, there is little point in high-effort replies, since no one will be around to see them.

At least Gemini (protocol) users are basically immune to this because of the obscurity of the system

Small communities. Usenet ~1990 was ~1m people with access, most at either universities or tech-oriented companies or government labs.

Amongst more general discussion platforms, HN, Metafilter, possibly Tildes.net.

Anything large is by definition popular and common, both terms with freighted meanings. The more so if they're advertising-driven.

Discord is still good as long as its a small server.