Thanks for voting on this issue and providing us with your feedback. We've revisited this suggestion, and unfortunately this isn't something we'll be looking at developing within the next 12 months.
From reading your comments, we fully appreciate that this feature is important to many of you. We're interested in understanding further why you want to mention groups on a page as opposed to sharing the page with them.
There are a couple of workarounds (mentioned by others in this thread) that may be of help to you in the meantime:
Jenny Millman | Senior Product Manager - Confluence Server