only sort of.
this is the original document defining markdown, and you’ll notice it doesn’t really specify a lot of the things that have compatibility issues across different markdown processors, along with allowing arbitrary html which really depends on where you’re showing it. There’s a list of ambiguous syntax here.
CommonMark is as close to a standard as we have.
some of them are also less bot detection and more spam limiting and mitigation. cloudflare’s has more stuff built in I’m sure, but things like mCapcha are just proof of work, so if you’re trying to make a bunch of accounts or whatever, it’s really computationally expensive.