If I can not attack a player with a different hero for 24 hours, it is not right that the same criteria doesn't apply to reinforcers. They should also have to wait 24 hours to reinforce with their other hero.
I agree with Mari. Different heroes of the same account and associated accounts should have consistent rules for use in attack and reinforcement. Fair is fair. And consistency is important.
Overall I agree, associated players should not be able to reinforce the same target because association feature was made to limit heroes of the same player to interact with each other, reinforcement is part of the interaction.