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.
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.
I never understood this.