send them the name of a file in your very old version of DOS?

Mine allows about an original tweet in length, but forces a line break in the middle, and it disallows dangerous characters. Just the usual suspects that always break everything and cause database tables to be dropped or commands to be injected. Exclamation marks are super dangerous.

I never understood this.

Honestly, I can understand stripping characters at a large organization like a bank. It shouldn't ever be necessary, but it protects against that brainfart/junior dev/marketing analytics software, with little cost.

What does that article have to do with comment fields on transactions?

It’s enough for a phone number, at least!