Some past exploits are allowed... I could name quite a few that folks are allowed to sell here. Ranger ingots, sigil hued items, tree ornament jewelry, etc.
The key things in determining whether a past exploit item is allowed by the powers that be are:
- How long ago it was fixed.
- How damaging it was to the community and the rares in existence.
- EA's stance on it.
- Whether items can be easily confused with true/current rares.
Items from current exploits are never acceptable.
That's how I see it as a moderator. If you would like to petition for something to be allowed, you can always present your argument via email to the admins and they'll review it. Hope that helps answer some of your questions.