Reverse Attack says that you reveal it during the Avoid Attack Step, but it doesn't say that the attack is avoided, so the Avoid Attack Step technically hasn't ended yet, which means that you should be able to use your defense.
There is nothing that says Sosruko can't Taunt himself.
If you can Reverse Attack a melee attack from an animal, I see no reason why a creature couldn't attack itself.
After all, it's not that hard to hit yourself...