Originally Posted by
bob sprocket
As far as I'm concerned space marines can use the archangels sanguine force. There's a couple they'll have access to, but nothing is game breaking.
The recent skitarii/cult mech/knight formation shows that the faction logo isn't defining of what faction models can belong to a formation (war convocation has a cult mech logo, but includes models from 3 factions). There is nothing anywhere that I can find that gives the symbol on the top of the sheet any rule meaning.