If you are a project owner, this is not the way to "reputably" market your coin to foster a community. It is recommended that you not do this.

If you are receiving these invites/getting tagged, then proceed with caution. This is a near-zero budget method of trying to bring exposure / publicity to a new coin that may have low liquidity or might get rug pulled later.

Personally, I ignore these. My logic is that I have enough invested in what I have already and that chasing pumps will get me no where and I find it equivalent to spam email.

Summarily, my personal recommendation is that you not go to those subreddits where you are tagged to join to check out a new coin.

EDIT: This could also be another method for hackers to try to steal your crypto. Some airdrops / presales require a web3 wallet to be connected / signed, I think, and this could be a method by which a wallet drainer steals your crypto.

EDIT 2: I'm making this post because I was tagged to join r/frencoin. I recommend you ignore these requests with my first edit in mind.