But why would one use it on a site that supposedly tries to dissolve problems using reductionism as a general heuristic?

It is no more a philosophical puzzle that needs dissolving than prices are a philosophical puzzle that need dissolving.

I am also using the term "free will" because people model their decisions according to that vague and ultimately futile concept.

I think that the concept of "free will" may indeed be more wholly a philosopher's invention, just as the concept of "qualia" is in my view wholly a philosopher's invention. But the everyday concepts from which it derives are not a philosopher's invention. I think that the everyday concept that philosophers turned into the concept of "free will" is the concept of the uncoerced and intentional act - a concept employed when we decide what to do about people who've annoyed us. We ask: did he mean to do it? Was he forced to do it? We have good reason for asking these questions.

But if possible (if I am not too lazy) I avoid using any of those bogus memes.

Philosophers invent bogus memes that we should try to free ourselves of. I think that "qualia" are one of those memes. But philosophers didn't invent morality. They simply talked a lot of nonsense about it.

Of course, it is real. Cthulhu is also real, it is a fictional cosmic entity.

Morality is real in the sense that prices are real and in a sense that Cthulhu is not real.

Some people talk about money in the way that you want to talk about morality, so that's a nice analogy to our discussion and I'll spend a couple of paragraphs on it. They say that the value of money is merely a collective delusion - that I value a dollar only because other people value a dollar, and that they value a dollar only because, ultimately, I value a dollar. So they say that it's all a great big collective delusion. They say that if people woke up one day and realized that a dollar was just a piece of paper, then we would stop using dollars.

But while there is a grain of truth to that (especially about fiat money), there's also much that's misleading in it. Money is a medium of exchange that solves real problems. The value of money may be in a sense circular (i.e., it's valued by people because it's valued by people), but actually a lot of things are circular. A lot of natural adaptations are circular, for example symbiosis. Flowers are the way they are because bees are the way they are, and bees are the way they are because flowers are the way they are. But flowers and bees aren't a collective delusion. They're in a symbiotic relationship that has gradually evolved over a very long period of time. Money is similar - it is a social institution that evolves over a long period of time, and it can reappear when it's suppressed. For example cigarettes can become money if nothing else is available.

And all this is analogous to the situation with morality. In both cases, there's a real phenomenon which some people think is fictional, a collective delusion.

In contrast, religion really is a collective delusion. At least, all those other religions are. :)

Can you give an example where the use of terminology derived from moral philosophy is useful instead of obfuscating?

The term "morality" is not derived from philosophy. Philosophers have simply talked a lot of nonsense about morality. This doesn't mean they invented it. Similarly, philosophers have talked a lot of nonsense about motion (e.g. Zeno's paradoxes). This doesn't mean that motion is a concept that philosophers invented and that we need to "dissolve". We can still talk sensibly about velocity. What we need to dissolve is not velocity, but simply Zeno's paradoxes about velocity, which by some accounts were dissolved as a side-effect of the creation of Calculus.

Consider the the trolley problem. Naively you kill the fat guy if you care about other people and also if you only care about yourself, because you want others to kill the fat guy as well because you are more likely to be one of the many people tied to the rails than the fat guy.

That is an example of the philosophical nonsense I was talking about. If you want to dissolve something, dissolve that nonsense. In reality you are no more likely to push a fat guy onto the rails than you are to ask for the fat guy's seat. In reality we know what the rules are and we obey them.

I don't see how it could be helpful to add terminology derived from moral philosophy here or elsewhere.

Again, the relevant terminology, which in this case includes the word "murder", is not derived from philosophy. Philosophers simply took a pre-existing concept and talked a lot of nonsense about it.

Consider the Is–ought problem. The basis for every ought statement is what I believe to be correct with respect to my goals.

Actually, I think that the use of the word "ought" in relationship to morality is very confusing, because "ought" means a lot of things, and so if you use that word you are apt to confuse those things with each other. In particular, the word "ought" is used a lot in the context of personal advice. If you're giving a friend advice, you're likely to talk about what they "ought" to do. In this context, you are not making statements about morality!

The person to blame for the confusion caused by using the word "ought" in talking about morality is probably Hume. I think that it was he who started this particular bit of nonsense going.

If you want to reach a certain goal and I want to help you and believe to know a better solution than you do then I tell you what you ought to do because 1.) you want to reach a goal 2.) I want you to reach your goal 3.) my brain does exhibit a certain epistemic state making me believe to be able to satisfy #1 & #2.

Here you're talking about giving personal advice to somebody. This is a separate subject from morality.