I had no idea that I could assign individual posts rather than the topic as a whole. I only found out about it from the responses in this topic here at Meta. If there is such a setting, I’d entirely turn individual post assignments off and only leave topic assignments.
I had a good usability feedback when I implemented up/down arrows to navigate between specific items in a longer list — worth considering this ui if you’re exploring ui improvement options.
Also note my other topic where I suggest adding a way to see all checkboxes from a topic in a single list. This comes from the idea that as you discuss something for a long time, you build a list of smaller todo things as you go. It’s very impractical to always go up to the beginning of the topic and edit it and add todo items with checkboxes. It’s much easier to add a checkbox in a message as the discussion happens, and then have the checklist to be formed and kept up to date and in sync somewhere (maybe in the first post!). So think of it as auto-TOC but for checkboxes.