The "read online message" feature for Steam doesn't work. It sort of makes sense since there are no online messages, but it is more broken for steam than for other protocols as when you right-click a steam contact, the icon (shown next to the "read online message") will be the protocol icon of the previous protocol you had selected. I.e. if you tried to call up the right-click menu for a jabber contact and then did it for a steam one, the icon will be the jabber icon.
Either remove this feature for steam protocol (as it makes no sense?) or check why it behaves so strangely.
@robyer/@unsane, did you have time to peek at offline messages on steam?
Thanks!