In the book's climax, Rico, a probationary 3rd Lieutenant with no real command authority, learns that his platoon sergeant has gone missing, and intends to go search for him. He orders the rest of his platoon to continue on mission without him, but they insist on going with him on the search and rescue despite his orders. While this is of course a Heartwarming Moment, it makes a certain degree of sense that they disregarded his orders to stay on mission: he has no real command authority anyways, making it the lead NCO's call instead.
Troopers was criticized on release in 1997 for having a very Beverly Hills, 90210-ish cast. Word of God said it was deliberate, and it becomes obvious why, since the film is actually supposed to be one big Propaganda Piece by the In-Universe fascist government. Naturally, they're trying to make joining the military look fun (hey, co-ed showers!)
The asteroid hitting Earth is often said to have been orchestrated by Federation. This doesn't look like it has much direct support from the movie except for the fact that the Federation is jingoistic and people want to expand into bug territory. However, after the Klendathu massacre, it becomes clear that neither the military nor the people generally believe the bugs to be intelligent; if so, then the Army couldn't have seriously believed that that the Bugs were actually aiming asteroids from half way across the Galaxy. The fact that a large portion of the population could both believe that the bugs are unintelligent and attacking them from across the Galaxy, just shows us how Double Think is in full effect.
In the early battle scenes, we see a lot of bugs with blown off limbs, still fighting. Then there is a break and a short PSA which points out the vulnerable spots on a bug. In the next battle, the bugs fall in droves with blown off vulnerables instead. This could be indicative both of the Show Within a Show nature of the narrative, or of the information being pushed out in the most rapid method available (mass media) after the Federation discovers a weakness.
Carl controls his pet ferret Cyrano ("Go bug Mom!"):
Carl: I gave him the impression that there's a grub crawling up my mothers leg, he's on a mission to go eat it. Carl's Mom: (banging noises can be heard upstairs) What are you doing?! GET OFF MY LEG!! AWWWW! ...Carl! Johnny: Carl, promise me you won't ever do anything like that to me. Carl: Don't be afraid. Can't do humans... yet.
A funny little scene establishing Carl is psychic, right? Later in the film, Rico - who had just ordered his unit not to go after Carmen, because she was almost certainly dead - is suddenly filled with mysterious certainty that she's alive and down a particular tunnel, going so far as to abandon his unit and mission, disobeying orders. And he finds her, as the audience already knew, in the clutches of the Brain Bug. After the Bug has been captured, Johnny talks to Carl, who talks about how getting the Brain Bug will turn the tide of the war etc... and Johnny, suddenly realising, asks him "It was you, wasn't it? You told me how to find Carmen." Carl basically winks and says "that's classified". Carl didn't know Carmen was alive. He had figured out how to "do humans". He was sending Johnny on a "mission" to find the Bug.
When Rico signs up for the Mobile Infantry, the clerk being revealed to be missing both his legs makes for an effective Wham Shot, but doesn't make much sense in context. Cybernetics in the ST universe has advanced to the point that fully functional artificial hands are a thing, so why aren't legs? They're much less complicated body parts in terms of dexterity or articulation, certainly.
This is from the book — the clerk does have perfectly useful prosthetic legs and he puts them on as soon as he closes down the sign-up booth for the day. He leaves them off while on duty so that any prospective recruits know exactly what they're getting into, so as to weed out the squeamish.