This screenshot has been reported:
Going to check the article 46101 you can read that all the programs that try to insert a code inside the game will not be supported (this does not mean that you will not be able to use Discord but that you will not be able to use the overlay functions).
This is because these codes are the same as using hackers to put cheat on the game (which of course Bungie try to avoid it in any way possible) and therefore, to avoid any kind of problem, they decided to block this possibility from being born.
This brings us to read the other quoted screenshot article, the 11929, in which Bungie consider it impracticable to use software that attempts to modify the code of Destiny 2 and thus confirming the possibility of being banned.
We understand very well that the intentions of Bungie are great, but does not it seem at least anachronistic to bend users for broad-spread programs such as video captures or voice chat outside?
Having said that, be careful and follow the instructions given to avoid problems.