Brandon, looked into the transaction you provided, and it's invalid. You're using WFS version 1.1.0 yet you're expressing the geometry in GML2 instead of GML3.
Unfortunately GeoServer is not telling us so, by debugging I noticed that the polygon was empty, this is because the parser skips over the parts that it cannot undestand. And as far as I remember, WFS insertions cannot be validatated, thought I don't remember the exact reason (I think it is because the wfs schema basically says that any kind of element can be put inside the Insert one, but I'm not sure, Justin?), anyways, the inability to validate them means also we don't have a way to report back an error message.
This fixed transaction works:
<wfs:Transaction service="WFS" version="1.0.0"
<gml:coordinates decimal="." cs="," ts=" ">
-121.663,47.464 -71.61,45.561 -98.829,27.526 -121.663,47.464
So the main problem here is not in the code not working, but in the lack of proper error reporting.... which I don't know how we can put togheter thought, unless we find a way to validate the xml before using it.
Justin, maybe the parser could mark down what it skipped and that could be used to report an error message in strict=true mode?