Originally Posted by scrapking
Silly question, how do you add the "Arc" tag to the thread?! I'm sure it's obvious, but I managed to miss it even so. And can I add it after the fact?
Not a silly question at all.
The prefix "Arc" is added when you choose it as a prefix when the thread is created. I don't believe you can add a prefix once the thread has gone on forum.
Once the thread has gone on forum, only a moderator can change the title of a thread and add a prefix. Just report your thread and send a request to the moderators to have a prefix added or to have the title changed.
I have added "Arc" for you.