That's good to know, but it doesn't apply here. There is only one verb - estás. Enojado is an adjective. See http://www.spanishdict.com/translate/enojado
I did a context search on estás siempre and came up with a lot of results which seemed to make more sense, and which probably would make more sense here:
¿Por qué estás siempre enojado? = "Why are you always angry?"
The context searches made it seem like either before or after the verb is just fine.
I don't know if it's a rule of Spanish grammar, but I never see a compound verb, such as "estás enojado" with an adverb embedded between the two parts of the compound verb. The adverb usually comes before or after the entire compound verb. The other two places where adverbs occur in a sentence is at the very beginning or the very end.
It could be. There's no compound verb here. There's lots of examples of estás siempre [adjective] in Spanish. See: http://context.reverso.net/translation/spanish-english/est%C3%A1s+siempre
Spanish adverbs never split two verbs that are working together. The adverbs go at the very end and/or the very beginning of a sentence Also, if an adverb falls within a sentence, it goes as close to the complete verb as possible, either before or after it, depending on the syntax of the rest of the sentence.
enojado is an adjective, not a verb. There is no compound verb involved here.
A few examples from a context search on estás siempre:
¿Sabes por qué estás siempre adormilado? Do you know why you're always sleepy?
Ahora sé por que estás siempre de vacaciones.
Now I know why you're always on holiday.
Con un vestido de baile tu estás siempre bien vestida. With the prom dress you are always well dressed.
Nos preguntábamos por qué estás siempre solo.
We've been wondering why you're always alone.
Porqué estás siempre dándome tu resumen?
Why are you always giving me your résumé?
Tú estás siempre trabajando o en la escuela. You're always working or at school.
There's a lot more at:
I wrongly put "why are you always stressed", and Duo lingo corrected me saying the translation should be "why are you always pissed" WHAT, i didn't expect that answer! Which is fine I suppose as we do say why are you pissed off meaning angry etc, so its not shocking, just didn't expect Duo to use it, lol wonder when the F word will pop up
Catch this: I mistakenly said "worried" instead of "angry" and Duo told me that the correct answer is: Why are you always pissed?
Aside from the low colloquialism of "pissed", in some circles it means "drunk, inebriated" not "angry". What Duo meant was "pissed off". That always means "angry". But I quesiton Duo's use of the word at all. Not that I'm offended - far from it. I got a good laugh out of it.
Okay, so you don't need the tu/yo/el/etc unless you're being specific between people...it's implied. Like I can say tienes queso, it means 'you want cheese' or 'do you want cheese' if you add the question marks. So in this case 'estas' mean 'you are' you don't need the tu to make it 'you are,' tienes has you built in.