Is there a way to block a Tildes user?

Edit: make purpose more clear

For the other aspect of blocking: (discouraging them from interacting with you when you won't read their comments anyway)

So, this is a relatively small community, and most people are acting in reasonably good faith (barring the occasional comment that needs a malice tag). If you assume that, you could just reply to a person and politely request they stop interacting with you.

I've had someone request I do that in a thread before. I did respond in turn and request that they in turn not make arguments about that (controversial and emotionally loaded) topic unless they were willing to hear polite disagreement, but immediately desisted from discussing the topic at hand with that person. I haven't run into them since, I don't think.

Continuing to argue or provoke a person after such a request would be easy to categorize as malice, and (I assume) people who repeatedly pick up malice tags are banned very quickly.

https://tildes.net/~tildes/wiki/customizing_tildes#ublock_origin

Ublock origin workaround

+1 in my case it’s a vulgar username, and Tildes doesn’t seem to have a way to change usernames, so engaging in discussion seems pointless (“Could you please delete your account and create a new one?”).