I know that this was marked as "not right now" previously... but that was in 2016. It's 2019 now, and removing history is a fairly basic functionality of most streaming platforms.
For me in particular this has become quite the issue, as my phone was stolen and the thief listened to a good deal of music that I personally would never listen to. My listening history now suggests that I might want to listen to R. Kelly again--the guy's facing charges for assualting underage girls, so I REALLY DON'T have any interest in listening to him, or seeing him in my recommendations, for obvious reasons! I've chatted with support about this and been advised to remake my entire account in order to escape the recommendations; frankly, if I have to make a whole new account to avoid seeing this man in my "time capsule" playlists, I may as well just sign up for a different service. It'd take the same amount of time and at least they probably have a remove from history functionality.
It's high time that Spotify lets us remove things from our listening history. I'm sure other people have past artists they don't want to listen to for various reasons--they clicked the song once and hated the style, they listened to the song with their ex and now hate it, their tastes have changed, etc--and tha ability to check "remove from my history" would greatly enhance the listening experience of all users, not just me.
Updated on 2019-02-26
As you mentioned, a similar Idea has also been suggested, and only one thread can exist per idea:
If possible, vote for it, and add a comment there, so it may be considered. Any update on the matter should be posted there.
For more info on how the Ideas Board works, click here. :)