I'd say you're more or less right about all of your points, but SN is young and those are all works in progress.

Bookmarks are great to reread posts n comments

You'd be surprised, lots of people go straight to the comments before reading the main post. I'm guilty of that sometimes, more so for videos, but sometimes articles and forum posts like these on SN too. Reading the comments can give you a quick feel of what the main post is about and you can decide if you even feel like taking the time to dig into the main post. It'd be a shame if some of the comments are deleted and the flow of the conversation is interrupted all over the place...