I've been doing this for over 20 years, and it hasn't really been a problem. During the occasional real-life interaction that requires someone to confirm my address and they express surprise, I just tell them that it's correct and I have advanced email needs. It never takes more than a few seconds -- nobody has ever said "please tell me all about your advanced email needs!" :)

> I use a password manager for passwords but I also need to use it to remember the associated emails.

I do this, too. It never occurred to me that you might not populate the email/username field -- it's kind of the password manager's job to keep track of that. :)

> The truth is no one really sells your email – at least no legitimate companies.

I think that on the whole, this is true. However, I have had a number of these addresses start receiving spam over the years. I think this is due to the companies' databases being compromised due to poor security. At the end of the day, the cause of the leak isn't greatly important, and I'm glad I can simply turn off those particular addresses.