First let's divide all the pilots into 5 groups:
Command - The FC / backup FC
Logistics - All the pilots providing reps to the fleet
Intel - scouts, spies
Mainline Offense - DPS ships
Auxiliary - Ewar, tackle, links, command dessies with jump fields
Command always has the gavel when it comes to being able to speak or interrupt on fleet comms. If the FC is giving orders, you should be listening and not talking. Prior to a battle, the Intel group is the second most important speakers on comms, followed closely by the pilots in logistics. During a battle, they swap positions with logistics being more important than intel.
Most of the time, Mainline Offense should be mostly quiet. When not in combat, they can use comms to ask quick questions or update on relevant info, but keep it to a minimum. During combat, these pilots should be silently broadcasting for reps or cap as needed, following instructions, and dying in silence as it may be. You die, type -1
Pilots in the Auxiliary should be almost silent for the entire battle, exception being calling out important targets being tackled, jammed/damped, or jumped off.
Things no one should ever ask/say on fleet comms during a battle is "where are you?", "I lost my ship and I'm coming back", "what should I fly", "I'm dying!!!", etc.None of that is helpful to the FC or the fight (unless you are bringing back a carrier or dreadnought that can turn the tide singlehandedly.
If you can't find the fleet in system, use Warp To in the fleet window to warp to a pilot you know is in the fight, like the FC.
Follow Comms Discipline and you'll be welcome in most fleets. Don't and you will be THAT GUY.