Is the intention behind repentance—seeking God's grace or His love—for the purpose of gaining people's affection praiseworthy or blameworthy?

There is no harm in loving the effect resulting from a righteous deed, and this does not contradict sincerity. The Prophet, peace and blessings be upon him, encouraged some righteous deeds by mentioning their worldly effects, such as maintaining kinship ties, which expands provision and prolongs life. Looking forward to the fruits of deeds does not contradict sincerity as long as the purposes of the Lawgiver are intended.