I think there's some value in providing a huge dictionary of things to test against, with tagging for what things are to help filter. This doesn't do a great job at it, and it would make 100x more sense as a library, but it's a little more than just string.contains().
My take on latency in general is this: You may just use the API to flag (not act) in an async way. This way, you can just alert/monitor and decide later whether or not to take any actions while keeping the flow non-blocking. Another approach would be to run it against existing handles to see what opportunities exist (ex: premium usernames, impersonators etc.).
Sure, but I’m not convinced that producing a blacklist and filtering system is that difficult. More importantly, it’s little things like this that slowly and insidiously degrade the user experience. Sure it starts with one 300ms API call, maybe most people won’t notice. But when you reach for solutions like this to every minor technical problem, the next thing you know it takes 5 seconds to sign-up.