Also, modifying your 3DS wont make Nintendo ban you, unless you give reasons to do it as using illegal pkmon in online battles and installing leaked game CIAs before their release date...
Unconfirmed.
Please keep in mind, we still don't have all the info on the last ban wave.
Yes, playing games online before release is the most likely way to get banned
But, every title you launch is logged, and despite your 'privacy' setting, it
may still be possible for Nintendo to see that.
Will they mass ban everyone using any homebrew/mods? Probably not.
But please don't spread misinformation.
Edit: Now, I should mention, that if you simply install b9s, and luma, and you limit yourself to only launching homebrew through the menu, and not a cia,
Then you're not really leaving anything log-able behind, but again, unless someone actually decodes all the packets being sent to Nintendo, we can't really be 100% sure.
But at the moment, that method is generally considered to be the most 'safe'.