Having TAB as Open Inventory button (on PC) is probably the most irritable thing to try to live with. In most - if not all - other games, Inventory was usually opened with E, I, or Esc. So in a confrontational moment like battling a ship, it's super frustrating to constantly remember to use TAB to swap ammo for my cannon.
At which point, I tried to look for how to remap that button manually to E for convenience sake, but apparently I can't change it! Why? It's one of the most unusual buttons to put an Inventory on, why not at least make it able to change/customize it? In a PvP game the last thing you want to consider is consistently trying to remember what button did what.
