If you paste text at the beginning of the input field that has a common prefix with the current text (or, simply, is identical), $.byteLimit gets confused about which part was there already and which is new. It doesn't seem possible to work around this without a larger rewrite, as we do not track this information. :/

Simplified test case:

• Have input with with bytelimit=12: $('#mw-content-text').replaceWith( $('<input>').byteLimit(12) )
• Have text in it "ążśó" (8 bytes, 4 characters)
• Paste "ążśó" at the beginning
• Expected result: "ążążśó", actual result: "ążśóąż"

Version: 1.23.0
Severity: normal