: : It would be quite a big step for the Sindar to "acknowledge" Gil-galad as high king as Tolkien reports in the Appendix. It is my opinion that it is just this sensitive political situation that caused Gil-galad to name Celeborn and not Elrond as his vice-regent of South Lindon which had a primarily Sindarin population. It would be politically "correct" for Elrond, as Noldo, to remain with Gil-galad as his herald. It would be quite another thing for Gil-galad to be perceived as appointing Thingol's "heir" to rule over Sindar.
: Which brings up the interesting question: Why didn't Elrond simply claim the Sindarian crown for himself? He obviously had the right to do so. Had Elrond been King of all the Sindar then perhaps Sauron would have been prevented from making The One.
One reason is that there doesn't appear to have been any sovereign Sindarin realms in the Second Age. I think Elrond would realize how pathetic it would look to be a king without a kingdom. He was not in the same position as his grandfather Dior who, although having to reestablish a realm, at least had something to start with. The only Sindarin settlement even reported is the port at Edellhond. I think after their experiences in Beleriand, the remaining Sindar sort of wanted to get back to their roots. So instead of trying to recreate a New Doriath in the east, they formed small communities in Eriador and east of the Misty's with no central administration. There simply wasn't a desire among the Sindar to recreate past glory. Some, as we know, entered Silvan realms and took leadership roles there but even they left the basic Silvan culture intact and did not try to turn those realms into Sindarin-lite.
Secondly, I don't see how Elrond as King of the Sindar could have prevented the making of the Rings of power. Celebrimbor was a Noldo ad Eregion was a Noldorin polity and if the high king of the Noldor couldnt stop him, what could the king of the Sindar do?
Russ