No one has been banned for homebrew, apart from online save editing
People did get banned before Atmosphere added creport but not since then (not for homebrew use anyway)
Still, you never know what Nintendo might do, one day they decide to take more direct action and implement code in a new firmware update to detect any CFW use. As you do need CFW in order to run homebrew on current firmware which was never the case on previous Nintendo consoles, that makes it much easier for them to detect. The new checks would be patched out in Atmosphere once people found out but not before damage was done.
That's why, if you don't absolutely need to run homebrew/CFW on your legit NAND, I find it best just to use an emuNAND for that stuff. People on 4.1.0 iPatched Switches don't have much choice though, if they want to go online they need to do so from an emuNAND, as the sysNAND can't be updated. People on unpatched or chipped Switches almost always have other options.
Of course that's just hypothetical, they could do it but that doesn't mean they will. At this point it seems like they consider it a lost cause and not worth investing money into, as getting banned would hardly stop pirates from pirating anyway, it doesn't really do Nintendo any good to invest time and money into banning more people if they don't get anything back from it. Investors might not be happy that Nintendo are spending money on something that doesn't benefit the investors bottom line.
But Nintendo are good at doing the unexpected when you don't expect it, and doing the expected when you expect something unexpected, so I never take anything for granted with them.
I care more about online than piracy (even if I don't play online much, I still benefit from automatic updates, cloud saves and all that) or I might not think twice about running homebrew on my legit NAND. But from the very beginning I took every measure possible to make the chance of me getting banned as close to 0% as possible so any risks, however small are not worth it for me.
That is also pirating if you not own the games you play in the emulators
Even if you own them it's still technically piracy if they aren't your own personal dumps. Morally there's nothing wrong with it though.