A design note you don't notice until you do, and then it'll annoy you forever:
Timelines in chat are usually forward-chronological (oldest at top, newest at bottom). Slack, for instance. And Slack correctly puts reply trees in forward-chron order as well, same as the conversation, but then maliciously doesn't scroll the view to the bottom, or remember where you read last. Typically incompetent but well-meaning for Slack.
Timelines in blogs and microblogs are usually reverse-chronological (newest at top, oldest at bottom). This blog, or Mastodon, or Micro.blog, for instance. I have comments set in the correct order here, but many blogs default to forward-chron when showing comments; it's unreasonable to put comments above the post, but I could see that making sense for "open threads". Mastodon's standard UI and the Amaroq iPhone client both do forward-chron. Icro iPhone app for Micro.blog correctly does reverse-chron, but Manton's Mac and iPhone apps both do forward-chron.
Why does this matter? A conversation is a filtered subset of all posts. It should flow in the same order as the overall feed. If it doesn't, you get whiplash, and avoid looking at conversations. Every time you open these wrong-way conversations, you have to scroll scroll down to the part you care about: New replies.
Maybe we should just make all microblogs read like chat, forward-chron everywhere. But out of habit and experience with chat systems, I frame forward-chron as ephemeral nonsense.
And now you'll be annoyed every time you see old posts at the top of an upside-down conversation view, just like I am.