These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Fan Wank: Hooooo boy. Let's split them into categories.
Not only is Covenant technology marvelously easier to figure out, but one OC apparently has the pull to completely redesign the entirety of the UNSC's weapons industry after spontaneously revolutionizing said industry in less than four years. He's not the Commander in Chief, just the head of one part of the Office of Naval Intelligence, yet he convinced everyone to stop production of normal weapons and retool the factories for his new weapons. Rather than design new weapons based on current rounds, he decides to completely replace the existing UNSC standard round - ignoring the fact that replacing the standard ammo of an interstellar nation would take years, even without an ongoing war.
The UNSC suddenly has smarter scientists than canon, and manage to massively improve weapons and armor for the infantry, vehicles, and ships. The UNSC goes from being a desperate nation outgunned, outnumbered, and outmassed by ridiculous margins to suddenly having a ship that can knock out several Covenant ships literally without a scratch.
There is a team of Spartan O Cs that has two members that are far too dangerous to be considered Bunny-Ears Lawyers. One of them casually leaves truly massive amounts of explosives just lying around, making his workshop a literal minefield that could cripple the ship if they detonate; that's not amusing and quirky, that's ground for a court-martial. The other one spends all of his time unable to stop thinking about killing everyone in sight, including allies, and is defended from a court-martial by his loyal misfit team members after nearly killing his own CO. In addition, he totes two weapons normally put on vehicles, carries a giant shield of titanium, and is capable of throwing said shield fast enough to slice through Hunter armor. How does he carry all of that stuff?
The level of detail that goes into the weapons is absurd. All you need to say is "it's a satchel charge", you don't need to spend a paragraph describing said satchel charge. If Jonathan's explosive creations are so amazing, why aren't they made standard issue? If they're worse than standard issue, then why is he using them? The sheer amount of descriptive detail is just unnecessary. Does Steven need to name his customized gigantic sniper-cannon?
Wa's augmentations in general. Genetic Engineering Is the New Nuke does not begin to describe what was done to him - which doesn't cover how the hell he manages to survive. Halo canon covered the Spartan II augmentations with the justification that the Spartans were selected for their genetic compatibility, and even then they lost roughly half of their number. Wa isn't a genetically enhanced soldier, he's a Terminator.