As noted above. If you have a size bbcode that covers most of a large post AND it has a list code in the middle of the post the size code is ignored from the list on.
An example can be seen at the link below in the 3.2 support forum. You can see the size of the text has been changed in the first paragraph but once it gets to the list code it stops. The closing size tag is seen in the post as it wasn't processed.