Great initiative. I had been thinking of something similar for the future as a proof of concept bot for the web3 stack I'm (slowly) working on, but ended up deciding on a port of existing bot code for my personal old-post upvoting bot instead.

Take care to keep things welcome-only, it is easy to drift into spammy behaviour. One tip: look into google's CLD3 to make things a bit more directed.

Using keyword scans, you are approaching it a little different than I would have ( I was looking into tapping into a small language model for both language detection and peer matching, I had no plans for communities).

There are decent python bindings for CLD3, and there is a wasm based javascript module too. It helps to quick language detection without a full language model, so you could personalize your message a bit for the new user and maybe use it to mix in some non-english communities and non-english posting accounts.

If you are interested in the base design I had in mind for my bot, I explored a more semantic approach. Instead of keywords, I was looking at using a Small Language Model (SLM) to weigh tags and language ratios against four-month activity buckets for active accounts. If you want to know more details of the base architecture I had in mind to evaluate if it might augment your bot, let me know and I'll elaborate.