I reported 2 people, and now their profiles say they have no achievements and friends. Banned?

They're probably using new accounts if they were banned. When you report someone it's best to block and forget. It also seems like Fortnite would be the one taking action if any were taken. At worst, they aren't playing Fortnite. Not on their original accounts. There are other options for them. PC or Playstation. Again, don't worry about them. Go play something! Happy gaming!

It's possible, there's no way to know 100% when another account is banned.

I tend to report people in Halo Reach all the time and they seem to never get banned too. I had even someone who was asking for passwords saying he could help people get achievements.

Most likely his friends won't do it. While many people have near 100 Xbox friends, most only have a few intimate ones that would be willing to do that. Besides that, if you are just reported for cheating by people that have never played with you, than Microsoft
won't ban you for it. I wouldn't worry about it. Many people say this out of anger and never do have multiple friends report you.

Why is Microsoft not taking this more seriously? It's a bigger problem than the enforcement site.. granted I said a bad word... but total ban going on a week? Seems disproportionate to the offense considering that I never had any action before... I have another friend that got banned for replying to a message with... "lol... gg"... the person reported that message and now he is banned.. so people have figured that they can use reporting as a toxic tool to ban people....