In my honest an personal opinion, It is very unprofessional, and not good practise!
There are many Ebayer's that follow the routine of ebay, but regardless, are punished by sellers withholding feedback, because they've come across a bad ebayer in the past!
Isn't doing this the same as saying, 'Buy my product, but I don't trust you!'This is exactly how it should work:
1. Buyer finds item, Makes Purchase, and pays.
2. Seller Dispatches item, and leaves feedback based on sale. (I.E. time of purchase, Communication, & duration taken to make payment)
3. Buyer receives item, & based on levels of satisfaction, leaves feedback according.
Don't fall into bad practise, If you as the seller feel the feedback you receive won't reflect your service, There an option to follow up the feedback!
Far more professional than witholding feedback and spreading bad practise!
Personally, I refuse to leave feedback for sellers who base their feedback on whether I leave feedback or not
(Ironically, the practise comes full circle, as this is what most withholders are trying to avoid), and If they still have NOT left their feedback 1 month after my item has been received, Then I leave neutral feedback with an honest account of the transaction.
IE: Excellent Product & Service, But Communication lacking, withheld feedback!