:
: It could make sense this way: The heir to the Sindarin royal house would be Elrond (as the eldest surviving male descendent of Thingol). He obviously recognized Gil-galad as his King. Thus the survivors of Doriath way well have been able to recognize Gil-galad as their overlord.

I don't see it that way. First of all, Elwing was there for quite some time and she was in no way below Gil-galad. Second, Elrond was of dual heritage. Through his father Ealendil and his mother Idril he was a Noldo and would certainly accept Gil-galad as high king of the Noldor.

That is an entirely different thing than saying he - or the Sindar in general - would accept Gil-galad as high King of all the Eldar in Middle-earth. The Sindar were not too happy with Noldor of any stripe after the sack of Doriath by the Feanoreans.

That sort of dual status we see in Elrond was quite common in medieval Europe where you could end up with some quite odd vassalage relationships. Elrond's would be similar - on one level (as a Noldo) he would be beneath Gil-galad on another level (as scion of Thingol) he would be Gil-galad's equal.

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.

Russ