bugzilla.mozilla.org now has a new “feedback” flag for attachments (bug). Use this like “review”, but for where you want to get someone’s input on a patch, and that input does not amount to a formal review. This is useful if the patch is a work in progress, or if the person you are asking for feedback is learning to do reviews in your component.
This new flag was Marco Bonardo’s idea and was endorsed by mconnor.
You can request feedback from specific people (obviously) and from multiple people at once. It’s available in all products and components.