welcome to our community, Pavane! I would also like to take this opportunity to apologize for the bad experiences and frustration.
let me explain a bit about clans vs factions. factions don't currently have any impact on the game (in fact, they're not in-game at all right now, though many players use them for roleplay purposes). they'll be used more heavily when co-op and adventure come around. the factions will be more driven by the game - it's a mechanic we set up within the game, and how well a faction does within the game will affect events in-game (that's my best understanding, at any rate - though I'm largely uninvolved in the development of our DLC, so don't quote me! but the point is, it's generally a game mechanic), while clans are driven by players for players. clans are simply groups of people that want to hang out with each other in-game, or teach, or compete with each other (and set up scrims to battle against other clans for practice), whatnot.
so if you're looking for people to play with, I would also encourage you to find a clan that is active in game around the same time you are active, and also is driven by what you want to get out of the game, whether that be hanging out with people and having a good time with good players, striving to be the best in tournaments, or to learn and maybe eventually teach new players yourself, etc.
for your original post, there are a couple of ways to know if something like that's happened. in the match chat in the bottom left corner, there should be a notification when someone joins or leaves a ship.
[Crew] (player name) has left.
I believe is how it should appear.
The tab key also shows the team/player list when you're in the match. Though it's not a notification; you have to hit the button to see it.
as always, I recommend suggestions be emailed in to us at feedback@musegames.com - they won't get missed that way, and they can be forwarded straight to the department it pertains to. I will send this one in, though