My understanding is that the highlighting parser _is_ fixed to intentionally mis-parse to guarantee reasonable runtime complexity, and the lint check is a band-

My understanding is that the highlighting parser _is_ fixed to intentionally mis-parse to guarantee reasonable runtime complexity, and the lint check is a band-aid on top of it for a common type of adversarial input. If you do the full parse you can end up with adversarial inputs that result in cubic or exponential run-time complexity (see, for example, Pygments CVEs for comparable examples in this domain).