As far as I understand, {makau} etc. are analogous to {ce'u}, except in {du'u} abstractions instead of {ka} abstractions.
That's an interesting way to look at it, but it makes it sound as if indirect questions can't be used inside a ka abstraction, which is not the case: {.i mi do simsa lo ka makau pluka ce'u}.
In this case, the indirect question places a focus on what it is that is similar between us. In fact, it delegates the similarity to pluka1 in such a way that the bridi is implying that {lo pluka be mi cu simsa lo pluka be do mobu} (mobu is a variable I assign to {lo ka mokau}. I have a couple other such variables: {dubu} -> {lo ka makau ce'u du}; {me'aubu} -> {lo ka me'au ce'u}).
Another example of ka-kau is {mi lojbo lo ka makau bangu ce'u}. Here there is an implicit claim that {lo lojbo cu bangu mi} and that that implies that {mi lojbo}.
{djuno2} is actually a ka, but we pretend that it isn't because the gimste made its definition clumsy to use that way. Indeed, the djuno2 is a property of the djuno3. (Why? Because you can't say "I know I like to swim about hamburgers.") When we use makau in djuno2, {.i mi djuno fi lo zarci fe lo ka makau klama ce'u}, (That's how guaspi's {djuno} looks like,) you're saying that you know what value will be returned by the abstraction-function. The abstraction here is a function relating a destination to the person/thing going there. We use "lo zarci" as an x-value, and {makau} signals where the y-value comes from. (In case you're wondering what a non-kau ka-abstraction returns, it's a simple du'u.)
As for the difference between direct questions and indirect questions, we take a detour into the world of natlangs. "I know who went to the store" is the translation of my most recent example. The word "who" there, despite being a question word when used like this "Who stole all the milk?", is *not* a question word under these circumstances. "Who went to the store?" "I know who went to the store." "When are you going to the store?" "What I do is more important than when I do it." The last example uses two indirect questions, which is far less clumsy in Lojban than in English: {.i lo du'u mi zukte makau cu vajni zmadu lo du'u mi cu'ekau zukte}.
.i mi'e la tsani mu'o