like when replying to a post you don't just need to supply the id of the post being replied to but also the id of the root post in the thread so you have to go and fetch the post you're replying to to find out if it has a root post
and whenever i've said "id" here it's not really an id it's a "strong reference" which consists of a uri and a hash & you get those after posting a post but you can't retrieve a post using them directly, you have to parse out the uri into separate components yourself
Of course of course as part of that you also have to do another API call for every mention to resolve the handle to a DID
God forbid it does literally anything for you