This users have registered more than 10 accounts and using each to post this malware link.
You can see this part in the malware link all the time to download the file: 1PHWncar2KSAXNMqeHSeH2f2seFR6pQ9B
Why is it not filtered and removed?
I think filtering links is a little hard, as they (scammers) can shorten the link, or change the appearance of the link, they can come up with some different keywords including link, which means if the admin has blocked a link with some "X" word in it, then scammer might come up with some "Y" word in it. I have no high knowledge of the technology, but might be via some scripts or extensions we could able to detect these posts from our sites, by delete I mean hide them.
The path you have shared might not be added in the ban list, as it can easily become useless, if some of the word changes in them. I wonder how these scammers are able to make 10 accounts, AFAIK we can't make account on BTT for free or if we want to make we have to pay some money if not in BTC then in alts via some reputed members, and we can also vote for some member so proxy ban would be lifted from there accounts.