Both reasons are correct, first the ink is much lighter than the ka"f, second indeed even if by mistake such a caf would be written bdieved this is not a shinuy tzura
I heard from a colleage that in sefer Mishnat Hasofer of R. Shtern there is a resembling picture that he pasels [I didn't check in the book to see what he wrote] I think even ca"f written with this blita, the caf is kosher bdieved and it is permitted to erase the blita and there is no psul of chak tochot involved
Is this because it is a dainty ink it is mutar to erase, what if it would be dark black like the rest of the ksav whould it be a shinui tzurah?
השבמחקBoth reasons are correct, first the ink is much lighter than the ka"f, second indeed even if by mistake such a caf would be written bdieved this is not a shinuy tzura
השבמחקI heard from a colleage that in sefer Mishnat Hasofer of R. Shtern there is a resembling picture that he pasels [I didn't check in the book to see what he wrote] I think even ca"f written with this blita, the caf is kosher bdieved and it is permitted to erase the blita and there is no psul of chak tochot involved