Pet Experience Penalty?

[Serendib]

Hello! I have looked for a definitive answer to this already on the forums but have been unable to find concrete proof one way or the other.

On Green Server:

Is there currently an exp penalty for pets doing more than a certain % of damage to an enemy while you are soloing?

I have been told that for example, as a mage, if your pet does 51% of the damage to an enemy while solo, you will lose 50% exp for that kill while solo. But that this penalty will not apply if you are grouped. Is this correct? It seems to be true from my experience, but I have no numerical proof.