If consecutive posts have no reply to post reference, I believe those could be safely merged together.
In addition, replying to the same post should trigger the merging action. IMO.
To enrich this useful suggestion by @OrkoGrayskull, such feature should have at least an option to determine time window during which consecutive posts meeting the criteria should be automatically merged into one message.
At our Discourse instance (~900 posts per day) there are a lot of users who are making consecutive posts (usually with media), rarely reaching the current max consecutive replies (which is set to 5 in our case), which really makes the experience reading the topics worse, but it is impossible to moderate it efficiently. We don’t know exact reasons for people not editing their post made 1 minute ago to add the new media, but there may be several like getting reactions or just laziness and convenience of making a new post.
Anyway, such a feature would certainly help heavy instances with extra active discussions.