The only time that eBay can see the IP address is when you generate the token. Thereafter your fine (although you may need to generate a token again at some point in the future)
The one issue that InkFrog used to have was how they hosted images. All images where hosted for a single user under their user ID. That means even if a single user had 4 eBay accounts linked to the single user ID then all 4 eBay accounts images would be hosted using the same user ID in the URL which can lead to linking.
It may well not be an issue anymore, but you would need to check the image URL between eBay accounts sharing a single user ID in InkFrog