Not a big fan of bots in general, especially ones spamming new users...
For this one I think you should make it optional. Give a command for everybody that makes them Opt-in to the reminder if they want to have it. How much you promote or credit yourself in the reminder is up to you I guess.
Optional is not really an option. (lol)
If they are unaware, how would they know they needed my bot in the first place?
now if we had only some sort of message board integrated into the platform... If you think the net benefit (for the platform) outweighs the spammy nature of your bot and you give an easy way to Opt-out then I guess I don't have much against.
I would use a wallet transfer instead of a comment, anyways.