I put this hypothesis to the test, examining 17 threads with 30 or more pages that are on the forum's front page (that is, the landing page when you click on Community from the main menu).
The results:
7 Threads were Play-By-Post Threads (both in- and out-of-character) (41%)
7 Threads were three or more years old and mostly continued by a single a poster (41%)
1 Thread was primarily about talking about other threads using increasingly strained pizza metaphors (6%)
leaving only 2 threads that matched your hypothesis (12%)
Basically, if you had a nickel for every (recent) thread that is more than 30 pages and that is, in fact, the exact same thread, inhabited by the exact same people, reiterating variations of the exact same argument, you'd have two nickels.
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In fairness, I think you have to exclude the PbP posts! And I'd probably exclude the single-serving posts as well (whether it's pizza, or undead origins) since those aren't really conversations.
In which case ... it's 100%.

(Fun fact- you can go into the subforums, like, say .... TTRPG general and do a filter to see the threads by number of replies.)