Interesting thread. In light of the findings mentioned there I will continue trying variations of Pt/Pd toning with silver prints. The archival aspect seems promising but I found the selenium toned print has a very different look from the Pd toned print I made and it did not just relate to the colour shift, there is greater contrast with Pd and more 'open' midtones.
Just as an aside, when I was looking for silver substitution formulas for Pt I came across this interesting web site that relates to Photographic Enamelling...
In this photographic process the silver must be replaced or there is a yellow staining of the final product.... As the beginning procedures are similar to many of the Alt Photo processes I found it interesting that they are also using the Cobalt Chloride process similar to what I had found elsewhere..