Threading in group IM's seems to be one of the more polarizing UX discussions that I've come across. A while back I was reading some of the discussions the Matr

Threading in group IM's seems to be one of the more polarizing UX discussions that I've come across. A while back I was reading some of the discussions the Matrix people were having about implementing a threading model, where it became clear that there were three very distinct ideas of "good threading" floating around: 1. Infinitely-nestable threading, a la Reddit and HN (and probably other sites first, but those are the ones I've used it the most) 2. Single-level nested threading, a la Slack (and maybe Facebook? I forget how much nesting they allow) 3. Discord/IRC-style replies (like you mentioned) where the responding message just quotes the original, possibly with a slight UI indication to make it easier to parse. I guess you could argue that Zulip-style threading is a fourth option, but IMO that's closer to a bulletin board than a group IM, because you can't have a message that isn't in a thread, so almost no discussion happens at the top level of a given channel. What's interesting to me is that the split between who prefers which style of threading is pretty close to even. I suspect, although I'm not sure, that it comes down to two things: the size of the groups in which you normally participate, and how closely-knit they are. A small, closely-knit group would likely prefer Discord/IRC-style threading, because sub-discussions are more likely to be of interest to those not participating, and the added noise isn't too big of a deal if the group is small. A larger, but still closely-knit group would probably prefer Slack-style threading, because even though sub-discussions might still be interesting to more than the immediate participants, but a single message space starts to become unusable with more than a couple of sub-discussions going on. A large and loosely-knit group is is likely to prefer Reddit/HN style discussions (and in fact those are two examples of large and loosely-knit communities) because a sub-discussion is less likely to be of interest to a significant portion of the main discussion's participants. Maybe, at least. It would be interesting to do a poll and see how those factors correlate.