It depends on how you implement things. There are definitely ways that you can double submit when hitting the refresh button, In those cases you probably will want a redirect in the first submit, so that it can't double submit, or maybe you are passing some value as a request param in xhtml, and therefore that value is in the URL that when you click the Refresh button is still there and double submits.
But I also know that you can avoid double submits. I think double submits is not really a Seam issue as a general Web development issue that I feel is easier to resolve with Seam.
I just read the TSS articles you referenced. I can positively say that Seam solves this problem. Once a Seam conversation is finished (i.e., the order confirm button is processed), you can still back into the conversation but if you want to click on the "confirm" button again, Seam will just redirect to a standard page you configure.
Of course, the PRG pattern is also well supported in Seam (through JSF). And as I said, Seam keeps JSF messages for you during redirection.