As http://bugs.jquery.com/ticket/9521#comment:24 points out, a simple "starts with <" rule will break some unit tests and is likely to cause issues in outside code. However, I think we should be willing to do that here for at least some cases.
The only issue I'm on the fence about is whether to trim leading spaces. I can imagine situations where people may have templates that end up with leading spaces, but then again it seems expensive to always pass the string through a regexp to remove them for the handful of sloppy cases that could be resolved by using
If people *want* to parse arbitrary complex HTML and they know it's HTML, we should encourage them to use the new
$.parseHTML method per #11617. It would be best if
$(html) didn't execute scripts for example.