Remove the limitation of 15 on the 2nd level of store categories.
Major review of the site categories - there are far too many categories with less than 10 items (many with zero items) and some with far too many items which need breaking down into further sub-categories.
Improve the dialogue following purchase. It’s messy and leads buyers of multiple items to pay for each separately.
As mentioned previously, kick off auctions where the seller hasn’t logged in for 3 months. He should get a warning after one month and another warning after two months. An alternative would be to quarantine auctions if the seller hasn’t logged in after 3 months so they are no longer visible to other users but if the seller subsequently logs in they can be easily reactivated.
Promote a system of buyer protection - how do buyers know it’s safe to purchase here?