Hey, first of all, welcome to elitepvpers, my friend! No, that's not a red flag. Of course, you can communicate exclusively through elitepvpers, but Discord makes communication much easier.
At the same time, I’d also like to point you directly to the

and
Among other things, they state that you should always send a trade request to your trading partner. In case any issues arise, communication through elitepvpers is also easier to track and verify.
Otherwise, feel free to reach out to me anytime if you have any questions!