Sure. Have you learned a new language recently? If you haven't, it's an illuminating experience -- usually you don't start with the idioms until you have a really strong grasp of the basics and of some other advanced forms.
I am not a native English speaker. In fact, I learned English very late in life. And I don't think you have to pretend you are talking to the whole world all the time and restrict yourself to simple English.
I don't understand, there's no pretending -- On Twitter, you are effectively talking to the whole world. Anyone in the world can click on your tweets and see what you're saying. If you want to have a broad reach, then minimizing the use of complicated words and language can absolutely help. That doesn't mean you can't discuss complex things, it just means being more deliberate in the way it's discussed.
So first, let's get the ad hominem out of the way. I speak 2 languages fluently in addition to my native language after living in 4 countries throughout my life, so don't patronize me.
Then, your argument is so silly that I wonder if you're just being contrarian for the sake of it. By your logic, anyone speaking language A should make sure to dumb it down as much as possible, make it extremely basic to make sure that anyone in the world who doesn't have a good grasp on language A can understand it unambiguously.
First of all, I don't owe you anything. If I decide to type a tweet in Italian, or Russian or whatever I don't have to accommodate you. If you don't understand the language, you're clearly not my target audience. Even though you can click on my tweet to read it doesn't mean that I need to make sure someone who doesn't understand the language can read it.
Second, this is a total disservice to people learning the language to not use idiom and common constructs. These are expressions people use in real life, if they are serious about wanting to learn a language they want to be exposed to them.