That's something for us to consider.
Most addresses are turned into links automatically.
Supposedly when you paste the website address into your post, it turns into a link automatically when you submit the post. The address needs to start with http though, not www.
There is a button in the panel at the top of the reply window which can add the http part if your address doesn't come with it already.
When I look at the ebay page, I don't see an http. But when I copy the address from there and paste it here, the http magically appears at the beginning for me.
Do you do that? Copy the address from your ebay auction and then paste it here? And then does it not turn into a link automatically when you submit the post?
Experiment here and let me know.