Profitable, whether for the company itself or for some oxygen waster to get some metric ("engagement"?) that justifies their salary/promotion. I'm not saying t

Profitable, whether for the company itself or for some oxygen waster to get some metric ("engagement"?) that justifies their salary/promotion. I'm not saying they will strip out the + from the primary email address used for login/etc - that would be dangerous for many reasons and could deny access to users. But they are absolutely likely to strip it out for obnoxious behavior which is only valuable at scale and individual failures don't matter - such as ad targeting, email spam, etc. In this case, it doesn't matter if you fail to spam the 0.001% of users with + as part of their actual username if it means you manage to spam the 2% that use + as an alias separator.