Cut network cables in Cisco 2960 PoE
Solution 1:
Test the ports thoroughly before trying to use them. I can't speak for your predecessor, but one reason I've seen that done (with cut ends or empty crimped ends) is to "mark" bad or sketchy/lossy ports on a switch; it's a great way to see at a glance that a port should not be used.
Solution 2:
It looks like the cut connector is being used to identify that as a port that shouldn't be used. I use a similar method but always use a non terminated connecter and affix a label or tag to the connector.
In addition, just to be clear, the physical ports (and cables connected to them) aren't "paired" together. They may be configured as a LAG, but their physical adjacency is not an indicator that they're "paired" together in any way, shape or form.
One final note, plugging a host into an empty port and seeing no activity lights on the port is not a guarantee that there is no activity on that port or that the port is disabled, shut down, faulty, etc. The only guarantee would be to run a packet capture on the host connected to that port and verify whether there's traffic or not.
Solution 3:
I've done something similar in the past.
I've taken an empty RJ45 plug, and crimped it without installing a cable (otherwise you might damage the port on the switch)
This was done on a switch that had a shared port, (i.e. a logical port that had both a fibre and copper port). There was a fibre installed in the fibre port which was the uplink to the rest of the network.
This was done because a while ago, somebody (who shall remain nameless), once plugged something into the port, reconfigured the port to the required VLAN, and then wondered why the switch suddenly disappeared off the network.
The most important thing here (which I'm guessing your predecessor didn't do) is to document why you've done it.
All our admins review changes to the systems documentation, and the blank plug serves as a physical reminder, just in case.