I somehow doubt he would say that. There is no direct correlation between trademarks and trademark words in a domain name. I could legally start a company making doughnuts and use the trademark XenForo to sell my doughnuts under. I would not be able to use the domain XenForo.com because it's already taken. But I could use xenforodoughnuts.com or XenForo.me.uk.
(NB: It would probably be a different issue regarding the actual artwork of the logo )
However I could not use xenForo.co.uk. Again nothing to do with trademarks but purely because that domain has been registered.
What Chris said here makes total sense.
XenForo ltd is not in a position to either "allow" or "disallow" the word in a domain. What I mean by that is they cannot stop you starting a company called xenforosoftware and from registering XenForosoftware.com as the domain is available. However if your company XenForosoftware is developing and selling software then I'm sure they would successfully sue your pants off.
So rather than thinking of xenForo "allowing" or "disallowing" it's better to think that of it as them not suing you for selling XenForo branded doughnuts (
@Chris D may be able to confirm that or not), but also that they disallow you from selling xenForo branded software in that your trademark within the same business class is confusing.
I think there may be a great area with a domain such as xenForosupport.com. In that case I think the word "allow" may mean that they are happy not to sue you as long as your site does not make it seem that it is an official xenForo site. Obviously you may want to use the actual or adapted logo and in that case I would definitely ask for permission and get it in writing.
I think there are often issues with game sites (forums) that obviously want to use the game's logo and character illustrations. Often the game company allows it if they deem it is helping but, but they could at any time sue or(more likely) issue a cease and desist and bang goes your Game forum.