Apparently, if you try to block your sword in ViaForge for 1.8.9, but changing the version to 1.9 or superior, the server won't see you blocking.

(On 1.9+)

(On 1.8)

thats because minecraft 1.9+ doesnt have blocking with swords

I know, but joining with a newer version of minecraft on a 1.8 server with ViaVersion allows you to block with a fake shield.

I know, but joining with a newer version of minecraft on a 1.8 server with ViaVersion allows you to block with a fake shield.

multiple layers of via* is not a good idea (if server version is the same as clients)

this bug happens because client viabackwards just doesnt accept second hand (so it is viabackwards bug/feature)