In turn, I don't think the limit is linked to bytes used via HTML.
Try quoting the table I posted twice in one post, see what happens

But you may have a point: I don't know how it's really stored internally in the forum databse. But it's obvious it gets larger than just the BBCode.
Well, I got curious about these limits and decided to do some tests:
https://bitcointalk.org/index.php?topic=5586893 
With the help of ChatGPT, I was able to reach the following conclusions:
- Based on your table, it's clear that the limit is around 29–33 KB, likely for tables. -https://bitcointalk.org/index.php?topic=5586893.msg66879700#msg66879700
- Posts should have a limit of approximately 4k BBCode tags -
https://bitcointalk.org/index.php?topic=5586893.msg66879788#msg66879788- I managed to create a combination of: 63,732 characters with 456 BBCode tags -
https://bitcointalk.org/index.php?topic=5586893.msg66879820#msg66879820- It is possible to create a text with 62,000 characters and 4,400 BBCode tags. -
https://bitcointalk.org/index.php?topic=5586893.msg66879843#msg66879843- I managed to create a post with 30,368 characters, 56 lines table/tr/td, 1,064 cells table/tr/td, 2242 BBCode tags, Contains only table/tr/td, table/tr/td, table/tr/td and their closing tags, Without color, size, url, right, b, etc. -
https://bitcointalk.org/index.php?topic=5586893.msg66879856#msg66879856Summary of tests performed
✅ The forum's 64,000 character limit is confirmed.
✅ The forum accepts messages with more than 4,400 BBCode tags, as long as they are not complex tables.
✅ A simple table with 56 rows and 1,064 cells works correctly.
It would be possible to test a few more combinations, as some types of tags can generate different limits. But I think this was enough to give us an idea.
Just so you know, I spent almost an hour working on this test. 