Resolved Maniphest tasks are rendered as strike-through when being mentioned in Maniphest comments.
I'd also expect archived Herald rules to be rendered as strike-through when being mentioned in Maniphest comments.

In Wikimedia we've been trying to reduce the number of active Herald rules to potentially increase performance.
One community member has listed all Herald rule numbers in a Maniphest comment via {Hxxx} markup, and it requires to click each Herald rule in that list link to find out whether it is archived or not.

I am aware that it's possible to query explicitly for (non)active rules via https://PhabURL/herald/ .
So this request is rather unimportant and more with UI consistency in mind. Feel free to decline. :)