Don't fall in love with your messaging in a vacuum
Messaging is tricky. You don’t want to change it all the time, but you also want to make sure you’re keeping your finger on your users’ and customers’ pulse and adjusting your message when things change.
You also can’t blindly follow every bit of feedback you get from your users and customers, but you do have to adjust and change your message when you’re getting consistent feedback that something isn’t resonating.
On the other hand, I think it’s very hard to evaluate your messaging based on metrics, like bounce rates or email open rates. Did your homepage bounce rate go up because your adjusted messaging is worse, or did it go up because you’re effectively repelling all the people who are a poor fit for the project/product?
Messaging — and the higher-level positioning it stems from — should be informed by your users and your customers. Don’t become attached to your messaging without validating it with people who are ideal users. In fact, don’t get too attached to it, period. Priorities change, and the message that worked 6 months ago might work less well now.
But don’t blindly follow your market’s whims, either. A major aim of a positioning exercise is to ensure that you are controlling the narrative around your product. You have to walk the line between incorporating feedback and ensuring you stay in control.