TLDR; killing a Summoner pet doesn't cause a player to corrupt, and that must change yesterday for the class to be playable at all in the current Ashes of Creation meta.
A Summoner's pet is vital to their Class, especially based on their role at a given moment. It's much more vital to the Summoner than their Mount is, for example, especially if they are healing for their group. Without it, you have no mobility spell, no AoE stun, you can't mitigate Damage with Bond, nor can you drain the pet for heals or mana. Despite this, an opposing player can flag as a combatant and kill your pet without corrupting, but killing a mount corrupts them. Highly illogical. Now, sure you can flag back and fight, but that is beside the point. If a Rogue flagged and killed your Cleric before stealthing away, they would at least be Corrupt now. There is no such penalty for the Mystic if they kill it. Summoners are a toolbox class that can fill different roles depending on need, and can solo efficiently as well. However, with this current loophole in place, you are essentially without PvP protection in any role you might need to fill, and pushing you out of a spot if you are soloing is easy if they know it is an option. Any Rogue can flag, Backstab your pet, dip (again, Summoner's only mobility is literally tied to the Pet, 0% chance of catching a Rogue regardless) and you have no realistic recourse whatsoever in many situations you will encounter in game where this can be abused; they just need to wait for an opportune moment. I've known this was a thing for awhile, but kept waiting for them to fix it, and was told today it is currently intended per Intrepid. At this point, we need to /bug this as an archetype to get them to take action. Being able to kill a Summoner pet without Corrupting is nearly equivalent to having a Summoner just lack PvP protection in its entirety, or at least leads to the opposition having no fear of reprisal. You can't safely heal for your party if you are on the Mystic; nor can you Tank or DPS. The pet is a huge part of several of our class abilities. It's currently as if anyone contesting you for a spot could Flag and kill your Cleric without Corrupting during a pull. It leads to extremely lopsided engagements for the Summoner, this must be adjusted ASAP.