Fortunately, watching the latest MacBreak #63 in which Leo Laporte and Merlin Mann cover TextExpander taught me not one but two useful things about this typing tool (three, if you count that I now know that Merlin has a mind-boggling 700+ text snippets). First is a handy way to control where your cursor is positioned once a snippet is expanded. All you need to do is include a specific string - %| - in your snippet to dictate where you cursor is inserted after your snippet unfolds itself. This is great for creating snippets in which you still need to include something specific on the fly that can't be snipped, such as creating [a href] links.
Once Merlin covered this hint, however, I was inspired to open TextExpander's Help file to see if there were any other hidden gems. While perusing their FAQs, I discovered an explanation to this aforementioned bizarre Dock hiding behavior (it's towards the bottom of the FAQ page if you're curious). As it turns out, the specific way TextExpander is designed to hook into Mac OS X has uncovered an alleged bug in the OS that causes this unfortunate drawback. SmileOnMyMac is pretty sure this is a bug in Mac OS X rather than TextExpander, and I hope they have alerted Apple, in which case we could hope to see a fix possibly in 10.4.9. For now, the easiest way to get around this quirk and hide/show the Dock is probably to right-click the Dock divider (the line between Applications and the Trash/docs/files sections) and use that contextual menu.