I think that multiple prefixes are a bit of a misnomer. If we were to implement a way to add multiple categorisations for threads, it would be in the form of a tagging system rather than multiple prefixes, which I believe would involve an overly complex user interface.
Yes, prefixes can be used like tags and vice versa. This is what IP Board is doing and I hate it. Because you can also use prefixes and tags independent from each other. My site will depend heavily on news with different categories, not just user content. I don't want to create 7 forums for separate discussion threads in different categories. I want only ONE forum where I post all the discussion topics to the main news articles (Wordpress) and then assign them categories via prefixes. My news won't be just single category news, but multi-category news, which means I have a problem if I can assign them one prefix only. You probably want now to argue that I could as well drop prefixes entirely and use tags. I will tell you why this is a bad idea:
Prefixes are meant for the most important upper categories/root categories while tags are meant for less important categories. Lets say I write a news about XenForo and vBulletin. I would assign the prefixes this way:
Users then know immediately that it's a news about XenForo and vBulletin. Since it's also a news about Mister X, Add-Ons and coding (which are less important than the XenForo/vBulletin categories), I would assign them the following tags:
You see multiple prefixes and tags can cleary exist with each other.
Wow... this is hilarious. Was looking for vBulletin multiple prefixes and this thread was the #1 position on Google, LOL!!!!!
I agree wholeheartedly with Kier. Multiple prefixes is a misnomer. The more appropriate term would be a taxonomy system to classify threads using different criteria in addition to the prefix. I am hoping to build that for our new Xenforo site.