We'd like some sort of <span> tagging to separate the various elements in a machine-readable signature.
I'd suggest trying to use web standards whenever possible. As a starting point, the [`<time>` element](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/time) around the comment time, with appropriate [microdata](https://en.wikipedia.org/wiki/Microdata_(HTML)) tagging to indicate that this is a [commentTime](https://schema.org/commentTime). There are similar [schema.org] attributes for [other comment-related data](https://schema.org/UserComments), although we probably shouldn't get *too* carried away. The semantic anchor for a user can either be their user page URL (ie, https://en.wikipedia.org/wiki/User:cscott) or by their stable user id (ie, https://en.wikipedia.org/wiki/Special:Redirect/user/173490 ).
We should also consider the issues raised in {T120409} as well. Parsoid's (former) semantic tagging about users is visible in 89f0eedf78173a0dcf343d5ab223c3da223c9201.