Is my router buyer screwed?

[oWell]

What about the guy that buys my old router on Ebay? Can he not log into Ebay or Amazon without getting linked and suspended?

[GreenBean]

What? Why are you responsible for his ecommerce behavior?As far as I am concerned you need to list a working router correctly described.
If he's being a cheapskate then.....

make coffee GreenBean, make coffee

I'd say if the router is functional and you are listing it honestly, why should you be responsible for what the end user does or does not do with it?

If the buyer will be using it as part of his ecommerce PC, the buyer should be educated enough to change from the default MAC anyhow. That's beyond the scope of your sale. Not your problem.