If you would point out some BBCode discrepancies, I would appreciate it. Some of them, I would be willing to accommodate.
As for allowing HTML in guides and posts, this is something that gets considered on and off.
I do intend on supporting HTML to some extent in the future.
According to the BBCode.org reference page,
http://www.bbcode.org/reference.php, we aren't using standard table coding.
We use "cell" and "row". Standard coding is [tr][/tr] for rows, [th][/th] for heading cells, [td][/td] for content cells. Using the correct code is important because there are HTML to BBCode converters online that aid in converting tables (which can be time consuming otherwise). They convert to the correct code which doesn't work correctly on DKPSystem.com.
The center and /center commands work here but there is no button on the bar.
In addition, many sites use the [left] and [right] commands for alignment.
In the end, HTML offers MANY more options for image alignment, linking, etc.