Seems to me that this particular point is being overplayed.
If I have someone on ignore, it's because I find them so annoying that I simply don't want to hear them speak, speak to them, or deal with them whatsoever. It's not like I have some deep seeded feeling that I must keep a book I once owned out of their hands. Is that really what "ignore" means to you all?
If I'm selling a book, Boardie A buys it, and after they receive it from me they hand it to Boardie B (who I have on ignore), why should I care? My purpose for ignoring Boardie B was fully served...that is, I didn't have to interact with them.