I don’t pretend to speak for the Church.
Because of a number of factors, the primary of which is the testimony of exorcists. Much of demonology is actually known because of information gained from exorcism. But I don’t think the Church is dogmatically defining those conclusions, either. The information is usually used to help exorcists and those whom they are ministering to.
The legalism bit is simple enough: even grammatical errors in Latin during exorcism won’t have the same effect as when those grammatical errors are not present.
Superstition is simply ascribing to a created thing a power it doesn’t have and which is proper to God alone. No, it is not superstitious to think that some symbols are associated with the demonic, and that using them could be perceived as an invitation. That would be a conclusion of spiritual theology that is either right or wrong. It would not be a superstition.
People who were involved in the occult are indeed more sensitive to this type of stuff. Part of that has to do with the fact that being involved in things like this can become a temptation in the future, and this is one way in which they are susceptible. Another part of that is that openly trafficking with demons leaves a certain mark on one’s personality, as I alluded to before. Most people don’t become possessed. But they can begin to acquire demonic personality traits. And yet another part of that sensitivity is very simple: folks who have been involved in the occult usually know more about how these things work than those who haven’t been. And this is especially true of those who practiced outright devil worship.
Nothing that I have claimed is a dogmatic teaching of the Church, as far as I am aware. But that doesn’t mean that it is therefore superstitious. The opposite of dogma isn’t superstition, right?
The power of the symbols isn’t in the symbol itself, and it isn’t necessarily in what the symbol means to any particular individual. The key is whether or not a particular symbol has been heavily used to basically worship demons with—and whether or not using that symbol in other contexts therefore gives a certain glory to the demon, and whether that action itself is construed as an invitation. It’s really as simple as that. You might tattoo a sigil on your forehead because you think it’s cool. The evil spirit might look at it and have other thoughts. If that symbol is his, he might begin to think he owns you. Should you mortally sin, and thus step our from under God’s authority, he might well be right.
Now, how that plays out in any given scenario differs from person to person. A lot depends on their personality, on their level of holiness, and on what God permits.
It’s absolutely silly to say that doing something like wearing an infinity symbol will lead to possession. But it’s not silly to say that an occultic image might attract special demonic attention. There’s a difference between the two.
Whether or not we should be concerned about it is a judgment call. I personally stay away from these things, because I have been involved in the occult, and I have my reasons. That doesn’t apply to everyone else because not everyone else has my weaknesses, nor I theirs.
Edit: By the way, I somewhat dislike talking about this, and so I’m going to have to bow out of the conversation. But you can absolutely feel free to have the last word, or to PM me should you have further questions or what have you.