User blog comment:RemosPendragon/Space Marines policy/@comment-10541616-20150903221411

I remember when there was a whole slew of loyalist chapters descended from traitor legion gene-seed, along with an entire coalition of said factions named "The Order of the Dark Loyalist", or something of that nature. I also remember this policy eventually coming into play and taking those articles down.

As for Loyalist Traitors... I'm not sure really. I mean the canon has examples of Astartes from the Traitor Legions fighting for the Imperium as the Knights Errant (whose ranks included Astartes such as Nathaniel Garro, Garviel Loken, etc), but that's the 30k setting, something we don't have much of here. As for the existence of Loyalist Traitors in the 40k setting... well you'd have to come up with a pretty contrived reason for them to still be alive after all this time without the assistance of the Ruinous Powers.

Honestly I think the general consensus is it's fine to write about all the Loyalist Traitors you like so long as their confined to the Great Crusade-Horus Heresy eras (like the article [Silvered Bladesmen] for example). After all, that particular setting is perfectly viable and for the most part untouched by the fanon.