Expedia developers don't know about RFC

TL;DR: Apparently, Expedia can't handle «+» in email addresses. Few month ago I used Expedia service to book hotel and used my email with «+expedia» tag, as I usually do, helps a lot with filtering. But with Expedia «+» breaks everything. It is few month already I can't unsubscribe from their spam. Two calls to support, «deactivation» of my account, but still I receive their ads. Funny thing is that «unsubscribe» link doesn't work. To unsubscribe I need to log into my account, which is deactivated. I could send all mail with «+expedia» to /dev/null, but seriously, WTF?