Quite aside from the topic of this thread (or in addition to), this, fersure.
It’s not just in e-mail addresses. It’s in text boxes in general, where, for example, a web site asks me to type in text – for any purpose whatever.
Take f’rinstance my HMO, which encourages communications by e-mail, but then delivers a mostly-well-developed web site but full of little quirks.
If I send an e-mail to my doctor, there’s a 1000-character limit to the length of the message I can send. AFTER I click on “send”, it checks for a variety of punctuation marks it doesn’t like and if any are present, rejects the message with a not-extremely-obvious error message. It’s clearly worded enough and lists all the punctuation marks that ARE allowed, but it’s just not that conspicuous. (And at least you do get to edit your message.)
BUT if I send a message to the pharmacy, it seems to go through a different system with all different rulz. The overall dialog is a little different; and the list of permitted punctuation marks is different. But the message can be 2000 characters long!
AND if I try to order a prescription refill on-line, there’s a separate dialog for that, full of its own quirks. One screen offers me a text-box in which I can write special instructions for the pharmacist – but it only allows 40 characters! :rolleyes: – only a fraction of what Twitter allows! They also had my mailing address wrong, with a rather quirky dialog to update that.