Hexbear developed an emote feature on their Lemmy fork years ago, and then converged back to Lemmy's mainline code in order to federate, so they have a selection menu that adds a little image. Anyone can add images with the picture feature (there's a button, or you can copy-paste and image), Hexbear just made a convenient list of hundreds of small images.

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You can also click the View Source button on a comment in the [more] options, if someone does something funky and you want to learn how they formatted it. Like inline code.