When a tweet is sent with a "&" characters, these get expanded to "&" by the API.
- When 140 ampersands are sent, an error is returned (tweet too long). Don't ask me why anyone would do that, but it does indicate a larger issue. For example, can someone with 139 characters and 1 ampersand still send the tweet?
- When a tweet is sent with 28 times "&" (equaling exactly 140 characters total), the tweet is sent successfully, despite the expansion of ampersands. The tweet in the API response has a length of 252, likely breaking implementations that expect a maximum of 140 UTF-8 characters.
- Inconsistency: when 140 ampersands are sent the API will error, but when 140 characters are sent with 28 ampersands there's no error. Both are 140 characters, so both should succeed.
I bet there are more inconsistencies with ampersands, but these two are "major" issues.