The only time I saw an agent get into trouble was back in my Express days. It was no secret that the mainline (USAir, in this case), held the commuters in open disdain, but I couldn't really help that.
So, I'm on this trip that double deadheads from base through CLT to MIA, as part of one of those random, holiday trips (Xmas, in this case) that winded its way back to CLT via MIA, TPA, and TLH the next day. So its Dec 23rd, and we get to CLT somewhere down on the C, to find that while our DH was booked correctly, there are no seats. The CA inquires to the agent, who states, loudly, "EXPRESS DOESN'T HAVE MUST RIDE", and seemingly ended the conversation, the clear implication that we weren't getting on the flight. This exchange delights me.
CA calls our Crew Scheduling, explains the issue, and they ask to speak to the gate agent, who promptly hangs up on them. Crew Scheduling tells us to just hang tight.
I sit down to continue my FO duties of not giving a flip, while I watch the hilarity of this impasse ensue.
So now we're down to departure time, and a supervisor hurriedly arrives at the gate, where a loud-ish verbal counseling session seemed to progress with said agent. There was some moderate hand waving. They pull two people off the plane, and we take our last row, middle seats down to MIA. I was mildly disappointed, because I was ready to turn around and go home.
That wasn't my last encounter with almost-blown DHs in CLT. I was there one day going through SVT (as it was called then) in the sim, and was on a DH back to TPA. Again, DH was booked correctly, MUST RIDE, back to TPA. I checked in an hour before departure, and patiently waited as the cleared just about everyone else. Finally, about 10 prior, I go up to the agent to ask, and he stated in a huff "well, we don't have a seat, so we're just going to send you to SRQ". I was near the end of my tenure there, so I simply said, "uh, yea, no, this is must ride". They had to pull someone off. I was completely indifferent to his annoyance with me.