Occasionally, links in comments that use MathJax do not show normally. The problem is reproducible, and browser-agnostic. It comes and goes depending on inserting a space around the closing
$ characters of a MathJax expression before or after the link. It occurs for
Alice $u $ Bob [link](https://stackexchange.com) Carol $v$ David.
I setup a demo on an abandoned question at crypto-SE. The rest of the present question is a picture taken from that page.