As someone who was banned I can say that Discord was not the reason I was banned (It was not running at all when I was banned). There has been some reports, apparently, that the overlay with Discord caused the bans for some people. After reading through everyone else's bans I have determined that there was not a single culprit. I would be inclined to say that just chatting with friends on Discord with the overlay turned off would be safe, but that's not accounting for other software that may be running on your system i.e nvidia's overlay that I believe was the reason for my ban. I didn't even know it was a thing because I never used it even though it said it was on after I scoured my computer looking for why I was banned. Bungie has stated, in their FAQs, that any software that provides overlays (inject code into the client) or certain streaming software can cause compatibility issues and will not be supported. No where does it say you will be permanently banned for use of said programs. I believe they mention that game capture on streaming software is not supported, but become super vague when talking about overlay software. After reading what Bungie has said I can safely assume this is due to over zealous cheat detection that they put into place and it was completely unintentional. Obviously this is pure conjecture because they have no customer support (sigh) nor have they replied to the bans. Knowing all this, it is still a small subset of PC players that were banned. If I were you I would probably wait until they release an official statement on what went wrong and their standpoint on it. There's nothing worse than buying a game and getting banned because you didn't follow their strict guidelines. Unless you are willingly to close every single piece of software running except for Destiny 2 to be safe. Essentially, no one really knows whats going on other than overlay software running in the background is probably causing bans.