I should have asked earlier, but how is this HTML getting into the RTF? Are you pasting it, or you are just typing and this is what InfoPath is creating?
the namespace is required on root nodes because of the XHTML requirement. I wouldn't worry about it showing up once.
However, the fact that attributes are getting duplicated (style, xmlns) is definitely an issue.
This could be a bug, and so if you could provide steps for me to build a sample form to repro the issue, then we can get Microsoft to get a fix for it for an upcoming service pack. Not that this helps you in the immedate time.
However, if there is something you are doing to cause this to happen, then perhaps we can find a suitable workaround.