[radlad]

Not surprised at all, I've been using the Internet and writing software for a couple decades now. Heck, I might've written one of the validators you're complaining about. But they are typically written to avoid +, for the exact reasons you described.

For those sites, you can add a dot in your username. Then you can ignore any emails sent to an address without the presence of a dot or a plus.

I'm sure there are sites that don't accept dots either, but I've never run into one. So you have to make an exception? Oh well.

I agree that it's easiest to do with [e-mail], like the grandparent suggested.

[centur]

IIRC dot is one of the characters that can't be discarded when checking local addr part (RFC 5322). So [e-mail] and [e-mail] are different addresses really. As far as I understand - it's a Gmail's team decision to configure local addr interpretation and allow `[e-mail]` and `[e-mail]` to be treated as the same address. I'd expect that dot trick rarely works anywhere outside of gmail world.

+ sign is part of the standard (`atext` token, RFC 5322), so sites, which disallow it in address are doing it wrong. The fact, that industry adopted a practice of using everything after + sign as a "tag" is not captured anywhere so this creates even more mess in already messy space (e.g MS followed GSuite in this too and added subaddressing - https://learn.microsoft.com/en-us/exchange/recipients-in-exc...)