5000-character counter/limit is inaccurate

[vaguerant]

Describe the bug
The character counter displayed under the comment field does not seem to accurately align with the backend character limit. Messages which the character count judges to have fewer than 5000 characters can still be rejected upon submission.

On which Mbin instance did you find the bug?
fedia.io

Which Mbin version was running on the instance?
1.8.1

To Reproduce
Steps to reproduce the behavior:

1. Start typing a comment.
2. Keep typing. My, you're verbose.
3. Stop at close to but less than 5000 characters.
4. Hit "Add comment".

Here's an example comment which Mbin identifies as 4961 characters long: severance-chinese.md

The above comment will not submit without modifications to reduce the character count.

Expected behavior
Either the post should submit, or the counter should more accurately track the number of characters.

Screenshots
N/A

Desktop

• OS: Windows 10
• Browser: LibreWolf (≈ Firefox)
• Browser Version: 136.0.4-1

Additional context
Using the above example comment, I was eventually able to get it to submit by editing it down gradually. I did some trickery like replacing > with > (no trailing space), replacing Windows CRLF with Unix LF line breaks and replacing ... (three periods) with … (unicode ellipse).

The comment would not submit at its original 4961 characters, would not submit when reduced to 4917 characters, and finally successfully submitted when reduced to 4881 characters. The limit thus fell somewhere between 4882-4917 in this case.