Sorry, I don’t use wefwef. In the main browser, you can navigate to the community and the “block” button is right below the “subscribe” option.

Near as I can tell, there are certain communities that have a “rule” that every time you browse that community, you must post something before you leave. This leads to a lot of low effort shitposting that I guess some people find fun but I just blocked those communities so my /All feed wasn’t cluttered.