I would split the two. Sincerity and sincere kindness are not the same and I would not expect the same answer.
Caring for others, when displayed long term, seems to provoke a respectful response in NTPs and INTJs. Too few ENTJs to comment.
As an Fi user, sincerity in emotions and behaviors, however, will evoke very contrasting results.
For INTJs, with tert Fi, my sincerity will be meet with a sincere response. This seems universal, thus I can be very open and honest with them. I can show happiness, love, caring, and pain, and they will respond in an accepting manner and extend forth assistance. They comfort me and I comfort them. I can trust them. We swim in fluffy emo oceans together. I show them more Fi than anyone else.
For INTPs, they mostly avoid everyone. However the ones that are my friends seem to appreciate sincerity. The ones very close to me, will read emotional pain I display and you can see they worry very much, but dont know what to do. They dont avoid it, they just dont know how to help. If I seem unhappy they will start telling me about technical projects that they know will make me happy. They appreciate the caring and courage I show to fight for the best solution for everyone.
For ENTPs, they love my emotional happiness, caring, love, and positive feelings. However any display of unhappiness or pain makes them shun me. So when unhappy, I actually can not be sincere around most of them, with the exception of two very close friends. It is something I have been observing and working the past few months. It is very subtle and I dont think they are aware they do it. Even changes of vocal tone or facial expression are enough to make them withdraw a bit. For me, it is not ideal as it is rejection of my Fi. The ESTPs are even more apparent about this. So sincere happy makes them happy. Sincere sad makes them shun me.
Fi can be used to manipulate other's emotions so perhaps this is a learned response. Perhaps Fi evokes feelings in others? I avoid many members of my family as they are Fi users who use it to their advantage.