Follow-up from "chore: Update multi-line suggestion docs"

The following discussion from !103231 (merged) should be addressed:

• @aqualls started a discussion: (+1 comment)

  @theoretick hey, you found some spiders! 🕷 I've had qualms about the Discussions (https://docs.gitlab.com/ee/user/discussions/) page for some time. (@phikai has heard me talk about this before, and probably @annabeldunstone too.) I don't want to hold up your merge request too long, but I do want to pause briefly. I've brought a discussion to TW team chat (slack link) so we can talk about the current state of the Discussions page.

  Capturing for posterity and transparency:

  I want to throw this question out to Suzanne and others with opinions about where we place subheadings in our docs when they match two topics. I have a MR from an engineer about multi-line comments in merge requests. I groaned a bit because my lack of love for https://docs.gitlab.com/ee/user/discussions/ is well known, but I want to get opinions from others—maybe I’m misguided?

  In this case, the subheading is about multi-line suggestions/comments in merge requests. Historically, everything discussion-related has landed on this Discussions page, rather than on the concept pages for issues / MRs / diffs / epics. I’m skeptical of the current placement, because to me, discussions feel like part of the user experience of issues / MRs / diffs / epics, rather than a standalone concept that users would be interested in.

  Where would YOU put such a subheading, and why?

  (Trivia: the commenting experience is mostly but not fully consistent across issues / MRs / diffs / epics. The inconsistencies are likely to continue growing, and at some point a decision will be required, not optional.)