Here is what you can put into the central invoice item info part for feedback:

<#AuctionSiteName> #<#AuctionID> - <#Title>

http://cgi2.ebay.com/aw-cgi/eBayISAPI.dll?LeaveFeedbackShow&item=<#AuctionID>&UserIDto=<SellerUserID>

I don't know why that blue penny oldtimer did not know it.