Hi guys. I'm getting ready to write a pretty extensive post.
Is there a way to subdivide my post into smaller sections and have those sections collapsible?
As far as I am aware,
NO. You cannot make it collapsible.
If your post is too long, and hits the character limits (per post), then you'll have to split it into multiple post. Otherwise, if you try to post it in a single post, it is likely that the last part will go missing.
Husna QA's monster topic is one of those example. Check this out and see how big it is. He had to make multiple posts to cover his content.
So my guess would be that some of this post is getting cut off due to posting character limits and its breaking the code wherever its cutting it off at and messing up the table(s)
Yeah, that's what it is. Posts over 65535 bytes get cut off at 65535 bytes. If that makes the BBcode invalid in certain ways, then you get the INVALID BBCODE error.
Also, note that a byte is different from a character. Because SMF stores "special" characters in a particularly space-inefficient way, each Russian character uses about 6 bytes, and each line break also uses 6 bytes.