my thoughts since I never really thought about it much are kind of like this:
contracts:
the contracts are typically mostly boiler plate specifying the type of contract, duration and similar.
retainer, raid security, garrison, training, etc. within some contracts (such as retainer) there is an enormous amount of leeway for specific duties as requested. much like most jobs today where there is essentially always: and other duties as requested.
I am sure there are distribution flags that can be set on contracts for a fee explicitly denying the release of the details of the contract to various parties for a period of time up to and including "forever" what this means is that the summary report might read like:
merc unit (A1254890) redacted has been retained by insert name (redacted) to conduct contract type (redacted) from the period of insert date range (may or may not be redacted) duties include (redacted) ....
and on and on, so when the target of the "raid" gets their requested copy of the "valid" contract, its not much more than there was a contract, and someone did it. there typically wouldn't be breadcrumbs for them to track down who it really was that did a hot drop into their city and went on a shooting, kidnapping, and raping spree they just know that someone did it and at least parts of the event was sanctioned.
now what they can always do is complain to comstar / MRBC that "someone" did actions on planet during times, and you would like to take out a contract and complaint, branding them as war criminals /pirates for "reasons" at which point the hiring party would get (shortly) as in up to a few months later notification that there is a complaint that one of their possibly retained units are accused of "insert complaint" at which time "someone" reviews the complaint and either laughs it off, or acts upon it based on the reputation THEY are trying to maintain.
as far as ratings, as I remember it, there are a number of factors that determining your units rating:
your specific unit size and type (doesn't directly factor in)
your units support capacity, (can you maintain and repair your unit) you get a higher rating if you can without outside resources.
transportation, (how much of your unit can you transport and to where)
technology when 3050-3055 rolls around the tech base of your unit becomes a factor, if you are rocking star league and clan tech you get a bonus on your rating.
mission history success and failure. successful missions (contracts) increase your rating failed ones lower it. you can also (as a unit) request arbitration if you failed objectives if they were not feasible to achieve, (basically you argue that your employer lied about the nature of the mission/contract, and that you tried in good faith to fulfill the contract) this can lower the employers rating and or impose sanctions on them if the review agrees with your complaint (as a unit)
being a member of a merc unit does not automatically absolve you of committing crimes depending on the nature, but shooting up a weapons emplacement MAY be considered when you blew up the apartment complex on the block that was backstopping it. unless you blatantly just opened up on the apartment building just because you could.
as far as data transmissions using the HPG system, I agree that "spam mail" as a general thing may or may not be a thing, (I suspect it is) but that a lot of groups pay for what amounts to local "markup code" based inserts.
So lets say someone subscribes to the "Girls of Tharkad" (hot girls on a cold planet.... ) magazine, if they get it on Tharkad it is likely to have one set of adverts in the magazine, if you receive it on luthien, or New Avalon, many of the adverts will be tailored to your current location at the time of receipt and depending if it is an ezine, or hardcopy, printed at a local printer.
as I remember it the charges for comstar service while somewhat high aren't really THAT bad.
factors were the size of the transmission (1 cbill per page of text) priority, and distance so if you are sending 1 page of text 50 jumps (roughly) that might cost 50 cbills at the standard priority rate, less as a just make sure it gets there "whenever" and more depending on the priority all the way up to: I want it there today... even if that means you have to wake up all the hpg operators this is an A1 emergency price is no object message.