I'm sorry if it came across as manipulative. One of the reasons for having it like this is also so it can give me a metric on who in the waiting list are most interested in the program. And of course also to offer an incentive to share it.
Re: Incentive to share it - Just build a good to amazing product - which the comments and upvotes you have on HN are already significant proof of - and you'll get higher adoption in the long run with exponential growth, without adding friction of little tricks like this which will be relatively inconsequential in the long run, other than perhaps causing friction with early adopters who will get turned off by them.
Maybe a quick survey with questions like, - what email client do you use now? - what is your favorite/least favorite feature of said client? - how often do you check your email? etc
Frame it as a reward not a punishment.