Thanks for the suggestions.
I muted them after a few weeks of class, then ignored them once the ability to ignore was unlocked for my account’s TL.
I continue to see all of their replies as collapsed links and their blank avatar under everything but my replies. There are maybe ten active users in the class, so hiding an avatar does little. They just become a user with a grey avatar.
From what I read in other threads, full blocking is intentionally not implemented because it is considered to be on the users and moderators to deal with this behavior directly.
I have tried to deal with it directly with them in private (they did not respond) and by asking the teacher if there were any private lessons or enrollment options. Maybe this kind of frustrating classroom use case was already considered in the decision to not implement full or mutual blocking.
From what I can tell, everyone else gets along with me and gets along with the other student. It is most likely a case two people not getting along in an online forum and being stuck together for the 10 month class.
Thanks again for the help.