I saw a different metaphor to the story, I wondered if Seb's situation might be similar to how Social Media can affect us. We start sharing posts and liking pictures from our friends and it feels like we're part of something bigger. A healthy balance might even give us a real benefit in terms of relationships maintained or grown beyond our immediate monkeysphere and we get a boost from the acceptance and praise that comes with being part of an active circle even if we can't get out as much as others yet we're still 'connected'.
For some people, though, it goes deeper. Eventually, they stop leaving their houses and having their own adventures. Their interaction with Social Media takes a turn for the worse where they start to define themselves entirely by this one small window to the world. As they dive deeper, it becomes a dependence and it starts to hurt them. They compare their own 'behind the scenes' lives to the 'best-of' reels for their friends and begin to collapse inwards. What once brought them join and acceptance now leaves them feeling like they're a lone swimmer who just can't reach the boat that's motoring away while everybody onboard parties, oblivious to the struggle in the water behind them. Their entire identity becomes wrapped up in this dependence, defines them, but insidiously, they feel they can't break free because then they'll miss out on more.
Seb tries to recreate that feeling of connection he had as a ship brain, to recapture that immediacy, that community the only way he knows how. He's someone who's been kicked off Facebook and is trying to see if he can fill that need with reddit. The outlet is different, but the drive is the same and the danger of losing himself to an unhealthy level in it is identical.
This story seemed less The Forever War to me than a parable about how we want to be helpful, social animals and how easily technology can refine and concentrate that desire to be 'connected' to a point where we harm ourselves.