I've been doing the + thing for more than 10 years now. My observation is that spammers simply don't remove it (it's just not worth their time). More important

I've been doing the + thing for more than 10 years now. My observation is that spammers simply don't remove it (it's just not worth their time). More importantly, legit services that are on the spammy side (or have broken unsubscribe links) will absolutely never remove it. Back a few years when Ameritrade had a bunch of its user's emails sold to spammers, I just changed my email on the ameritrade website and started blocking my +ameritrade address. It worked like a charm.