Tighr, try reading my bollocks again, I'm never clear enough.
Harry is a section head Screed.
he's in charge of Operations, which is that seat he sits in on the bridge, and all the noncommissioned crewmen assigned to work under him, or round robin shifts with him at the post. He's even in charge of the tourists who outrank him, but feel like slumming in Ops to get the end around on any staffing fatigue.
The smallest section on the smallest ship.
It's about the only way some one that green could get his own section.
Voyager got lost on Harry's first day of his first posting.
It's almost impossible that any one has less seniority than he does.
Putting a higher ranked officer in charge of Operations is a waste of that officers capabilities, but... Harry is in charge of the promotions process of all the crewmen working under him in collaboration with the XO and ships counsellor every 6 months.
(Do you think Harry rallied against Janeway to promote any of his staff?)
If Harry got promoted to Lt jg, he wouldn't be allowed to be the section head of operations, and would no longer be a senior officer. He would be part of a crowd of Lt jgs working under a Lt in some other part of the ship being of no importance whatsoever to the command structure.