version: 1.6.3
other: I'm OP
reproduce: i mount a untamed horse, when it is tamed, i see the zhorse message (.../zh claim to claim this horse ...) 2 times.

thanks

I could reproduce it but, as this is not urgent, the fix might takes a few weeks to come because I'm currently in an exams session

Does it still happen after server restart ?

yeah

Hello, I updated my main et test servers to the very last Spigot build and I can't reproduce this bug anymore, can you ?
(This is perfectly normal because there was no way that ZHorse was causing this bug)