The Ghostly Enforcement Team of Microsoft

You get to submit a case review but you only get one shot at it.  If they uphold their decision then you have to wait it out.  The easiest thing is to not break the rules so then you don't have to worry about suspensions. 

Have you tried to contact the Xbox support team via Twitter? 

And that's my issue, I should be able to make a case rather then them "review" evidence. Very one-sided and unjust. Won't have to worry about any of this on PC because Microsoft hit the fan on this one.

Support team has no access anything the enforcement team does. The enforcement team is literally hiding behind screens handing out unjust suspensions.

You can make your case though with the Case Review.

"You are about to submit a case for review. Please make sure to include any relevant information or facts before submitting."

"Case Review allows Xbox Live members to interact directly with XBLPET and gain greater understanding of the enforcement and why action was taken. In the very rare event that the review determines that a mistake was made or the enforcement was not necessary, steps will be taken to remedy the situation."

https://enforcement.xbox.com/en-US/home/howto#sub-topic0-6

"XBLPET investigates complaints and takes each report into consideration when making an enforcement decision, but a certain volume or frequency of complaints doesn’t guarantee a suspension. We take an evidence-based approach to enforcement and take numerous factors into account when considering issuing a suspension. The context around the content or activity is particularly essential and drives our decision-making process. Simply put, there is no magic formula that instantly results in a suspension."

https://enforcement.xbox.com/en-US/home/howto#sub-topic0-5

Sorry to hear you are having this problem, but not worth getting baited into anything like that. Report them and move on there's no need to reply any "unwanted" messages. 

Although, there's an option to turn it off if you go to: 

Settings -> Account -> Privacy & online safety -> Xbox Live privacy -> View details & customize -> Communication & multiplayer -> Others can communicate with voice, text, or invites-> Change it to friends only.

This is actually why people are recommended to simply block users or block communication from users not on your friendslist. If your found to be exacerbating the situation that can lead to an enforcement since you would have broken the code of conduct yourself.

This is especially bad when the user is using fake accounts to troll you into “slipping up”. I’m sorry for your frustration and experience and hope you have a better one wherever you end up. 

Let this be a learning opportunity however that it’s best to not respond to these type of trolls and, as hard as it is, try and be the bigger the person and walk away. What’s funny, is from experience having no reaction and leaving seems to make them more upset then when you try to respond 😉  

Here's the problem here, you broke the code of conduct by performing an antagonising action, that is that YOU made the decision to message them that you were reporting them, that in its own right is enough to warrant a suspension.  If you'd reported them and left it at that or done the even more sensible thing and reported them & muted and or blocked them then you wouldn't find yourself in this position, full stop.

You might be frustrated, and I totally understand that if it has went down as you've described it you have been wronged, however you too performed an action that is against that code of conduct which you rightly invoked against the other players.  As for the punishment against the other player, that's for the enforcement team to decide, if it's their first rodeo then a 24hr suspension isn't uncommon for that.  The reason you can't contact them as the likelihood is that they'd instantly become the target of unwarranted abuse, we see on a daily basis numerous threads like this where someone's broken the rules but doesn't accept that & most of the time, they're pretty horrid.  (For what it's worth this was relatively tame!)

As for Sony, well, they have similar ideology with regards to toxic behaviour, I can't speak as openly for Steam/Valve as they concentrate more on straight sales rather than moderating online play unless it's one of their own games & well they're pretty notorious for some of their punishments too!

Xbox support can do nothing with suspensions or bans.  That is controlled completely by the Enforcement Team.  

They can see all sorts of stuff behind the scenes. Threatening to get someone banned isn't allowed. That's why the rule of thumb is as mentioned. Report, block and move on. don't engage with people.