Make a note of their name, click on your (upper/right corner) avatar, then “people you ignore”, then add them.
I've ignored several hundred on this platform. I've got the threads watered down to the few people who actually know what they're talking about now. This forum is mostly empty when I open it up lol Obvious guy would say why do I ask this question then? It's because I need a way of blocking those who block their profile. Kind of a workaround as you will