How To @ Someone With a Hyphen in Their Username?

Well, that's exactly what he did but you missed the issue here. UnityAnswers does not use the whole username but only up the the hyphen. As far as I know there's no way around that. Actually the name matching is sometimes completely messed up. A good example is one of the Unity staff members "Graham-Dunnett". If you type the whole name or select it from the drop down the actual link would be to just graham which is a completely different user. Though it gets even weirder. Try just typing "Graham-" and it will match to grahadmills. As far as I remember this was broken from the first day on. Interestingly "Graham Weldon" has a space in the name and it matches correctly. Though the actual userlink has the space replaced with a hyphen. It seems that actual hyphens in the name are just stripped away because the actual user link to Graham-Dunnett is "grahamdunnett". Though typing the name without hyphen yields the linke to "GrahamDeanBraun".

So in conclusion: It just doesn't work with such names. UA is broken in so many ways I have given up all hope years ago that such issues will be fixed any time soon. The changes page hasn't change since 2015 as far as i can tell.

Feel free to file a bug report, contact Unity / QATO but I highly doubt this will have any impact on them. Unity now offers a paid support service and (at least to me) it seems they kind of left UA behind.

If you're really in need to contact a certain user, I would recommend to start a private conversation on the forum. (ps: I rarely check the forum, so expect a reaction time from weeks to month when you try to contact me ^^).