> 3. Post history being public meant that you could get banned/brigaded for your comments on a totally different subreddit (i.e. bots autobanning you on one subreddit for posting on another subreddit).

You can make it private now. Personally I think this is a bit of a misfeature since it ends up helping all the low-activity users showing up to post political agitprop in local subreddits, thinly-veiled advertisers, etc., but they changed it.

It's not really, you can just Google search and find all their posts and comments.