The following is an answer and/or comment by inhahe aka ColorStorm (inhahe.com - myriachromat.wordpress.com).
Yes, of course. A person's handwriting style doesn't just come from a vacuum. The development of a handwriting style obviously involves the person's mind, because who else is going to make the creative decisions that lead to one's handwriting style than oneself, and how would one do that without the us of one's mind.. so the end result is necessarily going to be reflective of certain dimensions or traits of the person's mind, and you can't separate the mind from the personality, thus it will be reflective of certain traits or dimensions of the person's personality too.

It's odd that anyone would think otherwise.. it's just a symptom of modern thought where everything is assumed to be separated from and uncorrelated with everything else by default until proven otherwise. But in truth, many, many things are connected, and a person is actually a highly holistic system so virtually everything about a person is connected or correlated in some way.

But anyway, even though handwriting style probably indicates things about personality, I wouldn't be surprised if most of what handwriting analysts think about what the relationships are is bunk. Just because neither handwriting nor personality is a thing you can easily systematically break apart and objectively measure its parts in order to verify correlations, so there's a lot of subjectivity involved, so of course people are going to make stuff up just according to whatever silly ways humans happen to think in.

Actually correct inference of mental traits from handwriting might be a really tricky thing that only a total genius, whose mind for some reason happens to be absorbed in the requisite dimensions of understanding, would be able to see.

And it may not be as easy as, for example, a loop of size X correlates to a personality trait Y, but that more abstract or derivative things about the handwriting which each affect every part of the handwriting might be what correlate to certain mental traits. And it may be that those mental traits they correlate to could only be understood as dimensions in a model of mind that doesn't even exist in popular thought.

It could also be that there are relatively few things you can accurately infer about the person from their handwriting. But there *has* to be *some* things you can accurately infer.

Edit: By the way, I read two books on handwriting analysis a long time ago, and all I remember is that they agreed with each other on virtually nothing.