The title says all, I don't want to see the 'goodmorning thread' and some others. Is there a way to mute em?
If you mean getting alerts from replies, unwatch threads you've replied to at https://www.seriousgmod.com/watched/threads Otherwise there isn't really a way to do so
If you're referring to unwatching a thread, you can do so by clicking "Unwatch thread" at the top right of the first post (pictured below). Otherwise, no, you will always see posts show up under "New Posts", you just won't get notifications for them unless you are watching them.
you can also change your settings here https://www.seriousgmod.com/account/preferences if you don't want to be auto subscribed when creating/replying to threads