Yes (0)No (1)
In fact, I suspect that changing to BBCode mode is what caused the problem in the first place, as that was what I used to format that post in the first place.
Since BBCode can't be directly interpreted by the browser, IP.Board (or any other forum software, really) parses it into HTML, but when encountering invalid BBCode it has to make decisions - you can't have a single post ruining the entire page, simply because a user forgot to close a tag. All the remaining closing tags will simply be posted as text.
The problem with the rendering of BBCode in general would likely be caused by overly complex and/or improperly nested BBCode. Simpler stuff shouldn't go wrong, since it's just literally a direct translation.
The extra closing tags are produced by the error itself; I did not type them.