A single thread can effectively slide from “hub” to “stub” and back over time, based on whatever latest news relates to that thread and the Ouija-like collective pull of subsequent group conversation.
Applesauce noted the model I’d call “shrub,” which is a “hub” until it grows lopsided due to a sufficiently large subtopic branch, which then gets trimmed off to become its own “stub.”
The rest are not worth inclusion in the survey:
“Flub,” a thread dedicated to a well-meaning but very simple question which someone then answers immediately via a nearly self-evident observation, thereafter rendering the thread an inert irritation until it falls off the first page and everyone forgets about it
“Club,” a thread started ostensibly to share an earnest observation, but really intended to toss an opinion-grenade into the crowd with the knowledge that the author’s claim to impartiality will annoy and frustrate others who disagree with the opinion being staged as accepted fact. See: this post
“Grub & pub,” wide-ranging hybrid of “hub” and “stub”: a general thread about a park’s food options which immediately becomes interminably gnat’s-ass laser focused on minutiae as soon as any specific meal, snack, drink, restaurant, or other food service area is mentioned by name
“Yeet,” a largely senseless thread, deliberately dissimilar from all others, used unironically-ironically-unironically to the annoyance of some, but which nonetheless wins nearly everyone’s hearts over time, and becomes celebrated to the point of being dropped into virtually any context to the general amusement of all participants