Sorry for the delay answering this. Unfortunately some of the features we created and some that we are planning requires our servers to have the token/key to operate on the blockchain.

I know that also without the posting key developers can always use the steemconnect token to broadcast votes or comments, but we NEED this in order to be able to let user schedule their post and have automatic upvote rules.

I also think that for a new application (like @steempeak) it's better to avoid storing the private keys, and much better to have the steemconnect tokens (that expire and can easily be revoked). I think most of the vote selling website do the same and also this is the same that steemauto do in order to be able to broadcast operation on behalf of the user.

If you know of an alternative method to do this please let me know and feel free to join our Discord channel ;)