A Sign of Trust (formerly Token of Confidence) can be sent from one player to another as a regular gift for friends or as a bid for acquaintance.
from Ladies[]
from Knights[]
Notes[]
Currently it is not recommended to waste rubies on buying Signs of Trust. As the "Social Network" button has no functionality.
And fixing it apparently doesn't have a very high priority for the developers. (Bug has been present for more than a year!)