I think the question is, how spammy would you think if 1000 other people would do the same? How relevant would the answers be if every answer would have 100s of answers from bots that are advertising their service?
Not sure why you're getting downvoted. "What if everybody did that?" is a great framework for considering the effects of novel behaviors.
literally is just Kantian ethics
I agree with the sentiment that this is borderline unethical, but I think that it's probably okay as long as there's a human in the loop presumably spending as much time/effort verifying the usefulness of the tweet before sending it as it costs the end user to read the tweet and decide if it's worthwhile.