I know it's safer,and we're encourage to use the forum's official escrow service
No this statement is wrong. The forum doesn't have an official escrow. And the reason most account are tagged for offering a escrow without track record is to prevent scam. You have to prove you can be trusted before applying to be an escrow.
OP you mentioned Offering escrow without a track record.
Do you mean no previous escrow track record or no previous deals/trades at all on Bitcointalk?
Theoretically, if a user wanted to become an escrow here, what would he need to do if he doesn't have a track record?
You'd have to do other activities that would make you deemed trustworthy by someone. Then that person would approach you to act as an escrow for them. Then if you did a good job for them, they would recommend you to other people. After a while, you would have a good track record and have many to vouch for you. At that point, you can offer it yourself. That's my guess, at least. It kinda has to drop in your lap, at first.