So I've been trying to figure out the tag auto complete thing, and the mystery deepens! It works when I post to other people's communities, but not to the comms I own, or to my own LJ. I haven't been able to find a 'switch' anywhere either. It isn't a matter of huge importance, it just niggles at me [g] I just have to figure out why things do/don't work!
If anyone is bored, can you see if you post to one of my comms, if the auto complete works for you? You can try at either highland_cross or holbycitylounge