Actually this is caused by using IceFaces' com.icesoft.faces.facelets.D2DSeamFaceletViewHandler ...arg
The default suffix is the page file (facelet page). The com.icesoft.faces.actionURLSuffix parameter is what appears in the URL. There is a limited number of actionURLSuffixes that you are allowed (seam, iface, jsf, etc), but the default suffix can be any extension name. (xhtml is what my IDE supports and is the standard by convention. Some of the sample apps for ICEfaces use jspx for use with other IDE's).
If you can post a simple sample app to the ICEfaces forum (or create a jira and attach it there), we can then see where the extension is possibly getting misplaced (misnamed?). So far, there have been no problems with the current D2DFaceletViewHandler (which may not be checking the context param when this situation requires).
Hmm... You are right that the OpenId component may have a little too much that is hardcoded. Please open a JIRA for any issues you are hitting.