A number of special pages allow users to enter a reason or explanation, but don't enforce a maximum length. Since the input is eventually limited to the maximum length (CommentStore::COMMENT_CHARACTER_LIMIT), and the rest of the user's input is cut off, the maximum length should also be enforced on the form.

Steps to reproduce:

• Add a reason/description of more than 500 characters
• Save
• View the saved reason

Expected result:

• Since the user could input more than 500 characters, they expect that all of the input was saved
• Actual result, only the first 500 (or 497...) are saved

Example: https://www.mediawiki.org/w/index.php?title=Special%3ALog&logid=19308485

Known forms without limits:

• Special:Tags (reason field, for creation, etc)
• Special:ChangeContentModel