At first I thought this issue was being caused by the Tag plugin, but further investigation shows that something else is going on.
When using the Tag plugin to close a tag when I type </ I am getting incorrect closing tags.
In this case I am trying to close the style tag.
In this case I am trying to close the script tag.
At first I thought it had something to do with the plugin until I disabled it and tried a few different highlighting themes. This theme shows the style tag looking a lot like the comment section above.