I think there needs to be a level 30 minimum for posting in Gameplay

I want to be clear about this up front: this is not because of new players. New players can and should have some way to ask questions about the game, and while I realize this would deprive them of the ability to do that in the Gameplay section, I think that GD or even a dedicated new player section would suffice.

This suggestion comes because of "forum accounts". These have a long history in League, being a prominent thing back in the original forums, and still persisting to this day. I'm guilty of having owned one myself. A forum account is basically a low level alt account you don't actually play on that you make for the exclusive purpose of using to post on the forums. The reason you would make a forum account is simple: it gives you access to an alternate name and/or identity with which to post on the forums with, while letting you retain (and potentially hide) your primary account.

Forum accounts really aren't a problem in most cases (I'd actually say they're relatively important to the culture of GD, and I wouldn't be surprised if they're very common on Roleplay), but they are on the Gameplay board, because a poster's background provides important context to their posts, and not just in terms of rank.

For example, being able to look at someone's OP.GG and see that they main a certain champion can give you a ton of insight into how they think or why they might have certain beliefs. If someone insists that some champion who really isn't that notably strong at the moment is super overpowered, you might question it at first, but if you see that their main is countered by said champion it'll make sense, and you can shift the discussion from one about that champion's balance to one about overcoming that poor matchup.

I think that in a discussion about the state of balance of League, or really any game, the participants in the discussion should know or be able to access each other's relative experiences with the game, because it is crucial to understanding each other's viewpoints. Posting under the same account name you play with is how forum users communicate that experience and show that they are arriving to the discussion in good faith. The use of a forum account on the Gameplay boards is an insult to the spirit of good discussion, whether the person intends it to be or not.