Why a Discord mockup looks different from a chat mockup
Discord does not draw speech bubbles. A channel is a flat vertical list: a round avatar, a username in the member colour, and the message text underneath, all on the dark background. That is why this tool renders a feed rather than the left-and-right bubbles you get from a WhatsApp or Telegram mockup, and why the result reads as Discord at a glance.
The input format is still one message per line. Starting a line with a greater-than sign marks it as yours, which switches the username and avatar colour. Everything else renders as the other member. Blank lines are ignored.