I kind of figured he traded the island spirit for Unseelie Magic. So I read it as him having that and Soulfire. I guess he wouldn't have had to. Harry seems to switch sponsors like I switch t-shirts though. I'd be calling shenanigans were I his GM.
Hmm, I missed any evidence of
losing the island spirit sponsor
. Need to re-read the books I guess.
As for shenanigans, I don't really see a problem as long as each sponsor is paid for with refresh. Don't think a second sponsor gives nearly as much a power boost as the first. It's more a case of additional options...and agendas.
I do think sponsor agendas should be emphasized. Else even one sponsor can cause an imbalance in power.