Why not? It's how Starfleet usually does things. It's not like this is anything unusual. You can apply that to most Starfleet ensigns. They're just starting starting out. You can deny it all you want, but Jack is Starfleet material, even if he is rough around the edges. Sounds a lot like his father who defied Starfleet orders to keep the Enterprise at the Neutral Zone, disobeyed direct orders from a Starfleet admiral with the Ba'ku, violated the Prime Directive at least nine times during his career... No one said you had to, but there are people who deserve the benefit of the doubt and not to be dismissed so quickly out of hand. Perhaps Starfleet isn't some long-believed Utopian organization after all...
Yeah, it is. The OP is calling for him to be second officer. That's not the issue. The issue is being second officer. And Picard was an ensign when he did this? Jack does not at this point. Perhaps when he is furthered trained to be an officer, and not just a jack of all trades living out on the fringes, but learning to work inside an organization and hierarchy. Until then, no, he doesn't deserve benefit of the doubt, much less 2nd officer of the USS ENTERPRISE.
And? If Starfleet or Captain Seven feels he can do the job, what's the problem? See above. If enough time has passed and he's moved up the chain of command, why can't Jack be second officer? Doesn't matter what rank he had. You said about having a long rap sheet of bucking authority. Picard has one too. In fact, it's even worse if he wasn't an ensign, because he should know better beyond that point, right? That's simply prejudging someone and deliberately deciding they aren't capable of great things. That's just consciously refusing to see possibilities. That's really not how Starfleet works and never has been shown to work that way. Starfleet has always taken in people with questionable backgrounds and given them the benefit of the doubt--like a Klingon, an android, and a Ferengi--and they've gone on to become fine officers. Jack helped defeat the Borg, one of the greatest threats the Federation ever faced, and that's not good enough for you?
I don't trust them. There, that's settled. Thus far no time is being presented, aside from one year past, he's an ensign, and second officer. True. I don't like Picard either. No, it's demanding that he serve time in grade rather than just being made an ensign and second officer. No, no it's not.
That's a personal thing, I guess. The OP didn't suggest that Jack be second officer while still an ensign. Matalas suggested a possible scenario in which Jack might have to assume command one day, but didn't specify when that might happen or what rank Jack would be if it did. Matalas was just throwing out a story idea, but nothing specific. See above. We don't know when such a thing might happen or what rank Jack might have at the time. It could be several years later, for all we know. Starfleet apparently thinks otherwise.
Then I'll wait and see and expect to be disappointed. Jack is underwhelming, at best. Starfleet has a long history of stable individuals in command: I really don't see why questioning a decision is such a big deal. I don't agree with Starfleet on Jack as a second officer. In time, maybe. Right now, no. A hard no. Right now it reminds me too much of this: Mileage will vary and clearly does because apparently Jack deserves all the doubt in the galaxy, plus free coffees for the rest of his life.
Given how quickly Starfleet goes through starships named Enterprise, Jack will probably be captain of the Enterprise-H within fifteen years, if not sooner...
That's why I said excused. And at least Nog actually went from cadet to ensign to lieutenant. Not cadet to captain like altKirk, or civilian to...second officer(?) like Jack.
The funny thing here is that In Matalas' original reddit comment, he actually never proposed Jack be the second officer at all. He just floated a "what if? scenario in which Jack wound up in command (or left with the conn), similar to what happened with a young LaForge in TNG's "The Arsenal of Freedom." So this thread title is actually misleading...
I personally think it would be far more interesting to have Jack be the renegade/rebel he is. Part of what annoys me about classic Trek is that Starfleet is presented as this godlike, pure, cultish organisation. Why does Jack need to be turned into another Picard? He didn't seem into Starfleet at all during the season. I think he's a section 31 type of person. To be honest, he reminded me a bit of Okona. Like, that is not your captain...
No? The captain can order whoever she wants (within reason) to take the conn. If there's some reason that Seven thinks Jack would be the best person to have decision-making responsibility over the ship (say, he has some experience with the aliens or planet they're dealing with that is unknown to Starfleet at large), it doesn't matter if he's the five hundred and fiftieth officer, she can put his butt in the captain's chair until she gets back.
I think it's far more likely that the second officer is Mura. He should be a lieutenant commander now after everything the Titan-A/Enterprise-G bridge crew went through.