If you switch to Tridactyl [1], our buggier, less popular, and less user friendly competitor to Vimium, you can pass hints CSS selectors.
E.g, `hint -c a+a+a` only highlights comments on the HN homepage (and every third link in a row on other pages). I have it bound with `bind ;c hint -c [class*="expand"],[class="togg"],a+a+a` which also lets me toggle comments on HN and reddit.
It brings vim-like shortcuts to your browser. Despite what the Readme says, I find it perfectly usable on Firefox.
[0]: https://github.com/philc/vimium