Hey Nitoo,
What you have written could be true to an extent or possibly could be THE reason for Angad for putting sindoor on Kripa's forehead.
My reasoning for Angad's act is as follows:
Let us examine some facts,
Angad is already in love with Kripa.
And he is in complete denial of it.
Angad is aware of the fact that Kripa was deeply in love with him once.
Angad is also aware of the fact that Kripa still cares very much for him inspite of all that happened and she is ''possibly'' still in love with him.
Angad knows that Prithvi is deeply in love with Kripa.
Angad is confused over Kripa's feelings for Prithvi, although I feel that he is sure that Kripa is not in love with Prithvi, Angad is in doubt whether she might be using Prithvi to get back at Angad (which obviously is untrue) and make him jealous. Hence, when Mishti told him yesterday that Kripa had acknowledged and accepted Prithvi's feelings for her, Angad was so shocked and angry! Shocked because he was under the assumption that Kripa holds no feelings for Prithvi and angry becasue despite still being in love with Angad, she apparently accepted Prithvi's proposal, whatever the reasons.
Hence, after viewing all the above fact, what I can make out is that Angad, overcome by a mad rush of possessivness and confused emotions, will put his stamp of love & ownership on Kripa, signifying to her that by putting Sindoor on her forehead, he has made Kripa his forever...........
(Kripa had told Angad that when a man puts sindoor on a woman's forehead, he commits not just himself to a relation, he also binds the woman for her wholelife to him)
My two cents!
Cheers,
Chilly