I don't know if anyone else is experiencing this but then you click on the BBCode Mode Icon Top Left hand corner make a few changes then click back to normal editing the font face and font size tags appear in I have done so in this exact post to show an example.. but oddly enough it only happens when editing a post not creating a new.
As long as I'm not going out of my head while I was typing the OP it wouldn't do it. but I'm not using taptalk. Edit: Seems to only do it when other elements are displaying like links and images [background=#fafafa] [/size][/background]