Yeah. Zalgo text is a common test for input fields on websites. But it usually doesn't do anything interesting. Maybe an exception trigger on some database length limit. Doesn't typically even kill any processes. The exception is normally just in your thread. You can often trigger it just by disabling JS on even modern forms, but,, at best you're maybe leaking a bit of info if they left debug on and print the stack trace or a query. Another common slip-up is failing to count \n vs \r\n in text strings since JS usually usually counts a carriage return as 1 byte, but HTTP spec requires two.

unescape(encodeURIComponent("ç")).length is the quick and dirty way to do a JS byte length check. The \r\n thing can be done just by cleaning up the string before length counting.