My point exactly, symestreem, It would make more sense to do so. If The Eldar, with there linguistic talent, could teach the horses the languages of Westerness and others, that way there would be more understanding between horse and rider, and a horse could tell someone to get off them if they did not wish them to ride them.
Besides, Orome may have thought his horse to comprehend the tong that he used (would that be Valinorian or something like that?) And Nahar being the father of the Mearas could have passed on the knowledge to his offspring, who passed it to theirs and so on. Plus the fact that the Mearas had to breed with other types of horse, the linguistic skills they had may have passed into other breeds also. If this is so, then this may explain why the Rohirum had such a close bond with there horses, Maybe, even if the Rohirum were not aware of the fact that the horses could understand them, that would be the reason behind the amassing faithfulness of the rohirum's horses.