Great! Thank you for letting me know. Any chance of supporting something like that for the wiki pages too? So that we can refer to other pages or headers in those pages using @ or # mentions?
We have no plans but feel free to make a feature proposal.
Can I mention comments on issues or review?
If you copy-paste the URL for a specific comment into a new comment it will show as `#123 (comment 234)` and link to that comment. There is no special reference syntax to link to a specific comment, because it's much more likely that you have the URL to a comment on hand, than just its ID :)