For a hyperbolic example, imagine you had a partner who wanted you to lose weight because you'd got fat and found you unattractive as a result. They choose speak kindly to you about how they feel to see whether they can change your behaviour, and own the possibility that you're not interested in what they have to say.
Is this <em>no different</em> to them using some subtly crafted speech (based on their in-depth knowledge of your insecurities, etc.) which creates some shame or self-doubt, whilst not making their real position or motive clear?
Or equally, one of your children's friends wants them to try a new legal high; in case (a) they describe how they find it and what it's like, and in case (b) they use some social pressure about how everyone's into it and it looks cool, etc.
Or you go to your doctor, and she offers you a new drug for your ailment; in the first case she describes the evidence base for it and any potential down-sides in statistical terms you can easily appreciate. In the second, she conjures an image of your ailment worsening progressively until you are a drag on your family and you die resented and alone; this is a possible but unlikely outcome if you leave the ailment untreated.
In all these examples the two paths are no different in terms of someone trying to influence someone into trying something out, but most people would find the first options preferable to the latter.
I think the point is not that all attempts to change someone's mind are manipulation and so completely morally equal, but that some kinds of manipulation are hurtful in themselves either because they are deceptive or because they hurt people.
A show HN post may be trying to manipulate you, but hopefully it is not using deceit or an emotional over-reach to do that.