In the squirrel girl PvP I was hit by MercyEhm so I retaliated them. On finishing I saw them still there as a retaliation node and assumed they had hit me again but the notification was laggy in arriving so I hit them again. On finishing the second match there was still no notification of them hitting me a second time and they were STILL there as a retaliation node.
As much as I might want to test if the effect is permanent it seems kind of mean to keep hitting him over and over again in the name of science.
EDIT: For extra info… I had 2 retaliations saved in the other 2 visible nodes and there were no other retaliations queued behing MercyEhm. If the system was working I would have a fresh node to replace him and still 2 saved retals in the other nodes.