1) Sebastos doesn't respond to "Rally Carrier" command, even when it's the only carrier in fleet.
Currently in Starsector's game engine, you have two choices: a ship is a carrier, or it isn't. Regardless of how many flight decks it has or what its name or class is, there's a flag to either be ignored or positively set that states whether the ship is a carrier. A ship that is not a carrier behaves normally, entering fights as one would expect of a combat ship; it does not respond to Rally Carrier points, and basic move orders are given as Rally Taskforce. A ship that
is a carrier behaves extremely cautiously, skirting the edge of the battle and attempting to avoid any credible threats unless given direct orders to hold ground or attack; it will respond to Rally Carrier and create those points when ordered to move. Thus, generally only ships designed around being a hangar with defenses get flagged as carriers, while front- or mid-line combat ships that have a "bonus" flight deck are not.