I wouldn't call this a bug, but a major annoyance. At this point in time, when making an edit to a thread, you are able to edit the tags associated with said thread. This can be a headache, as choosing a forum category when first making the thread autotags it with whichever category you choose. If you do not remove the autotag, let's say #destiny, then all of your edits will be denied and removed as you cannot place a forum category in the tags section, you can only select it from the dropdown. Rather than this error being a popup, can it show up as red text above your freshly edited body with a red asterisk next to the offending error? While I've learned to go back and delete the offending tags before posting... It is rather annoying losing four paragraphs of fresh material due to this small error (on my part)
Definitely an annoyance. When trying to edit a thread yesterday I was prompted with the above message - which is the same issue. I think there should be an easier way of avoiding this.