Skål - Cheers - Gom Bui - Prost - Almien - Salut - Kampai - Na Zdrowie - Gan Bae - Qapla
Yes, you can. It can be worth doing to get more Ragnarok points, or to achieve quests.
Or to lock down a Province for next Age. Or prevent an opponent from doing so. Or a variety of other tactical reasons.