If you really believe that you were banned for promoting Lemmy then you should mention this in your appeal but as others have mentioned it seems like the issue was spam.
And that's precisely why the issue is going to be 'spam', even when it isn't. Because if you can't get away with stating the real reason the ban went into effect, you're going to do it under the auspice of something that has a degree of plausible deniability. I'm far less willing to give Reddit the charitable benefit of the doubt on this, seeing the shear amount of ridiculous bans that have been given out to people. But who knows, it's entirely possible it could've been spam.
Izzy