"Yesterday he had written the letter."
Translation:Hieraŭ li estis skribinta la leteron.
so in a way using the suffix inta onta anta indirectly beefs up estas and makes it have direct objects? or am i misunderstanding the "n" here (because the only verb i see is estas which shouldnt be acted on by the adjective "skribinta")
"skribinta" is a special kind of an adjective which is called "participle" and yes, adjectival participles can have objects
dankon! Jus nun mi estis dankinta vin ...mi deziras komenti al gxi...? thanks...just now i having thanked you desire to comment on(to)it?
It would mean something like "having thanked".
"Mi estis dankinta vin" would be "I had thanked you" (I was (estis) in a state where I had already (-int-) thanked (dank-) you).