What can we possibly do about this?
Do not spam. To quote from the One Stop Rules Shop, spam is "making a post that doesn't have any sort of use." Of specific note when talking about spam, large images are spam if left un-spoilered. This means that if you want to post a GIF, or some other kind of reaction image, it either needs to be spoilered, or you need to make sure it is small. Also in line with spam, garish posting: Don't do it.
Personally, I feel that TET's rules on spam are not adequate enough. Whether or not a post is useful is a subjective matter, therefore those who read it will post as they see fit as opposed to posting by moderation's rulebook. Maybe outline that posts which just say "hello" clog up the thread and so it counts as spam? Because as I have already said, a thread that calls itself "a space to just chill out and talk with each other" will naturally be full of these as people will want to talk to each other in a natural way on here! Many of us have formed friendships on TET as well and so when we see particular users online we are likely to greet them.
Maybe this is a bit too wild of an idea, and I don't even know if it would be technically feasible, but maybe you could introduce some sort of minimum character limit for posting on TET, or even NSG in general? Like that, we would all be prompted to say more than just "hi" while blatant spammers who go "hiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii" can easily be dealt with.
I'm kinda pissed that TET has been locked, and so in future I will regulate my posts better so no F&-esque stuff lands in TET. But as I said, something really needs to be done about clear communication of what's fine and what doesn't fly.
Pretty sure this echoes what other users and the OP have said, but I just wanted to throw my own thoughts into the mix.













