With no context, we cannot say definitively that farbi or pentri is better, or choose between murojn and vandojn. But the point of interest here is the syntax (not lexical choices).

The 'solution' is to use a preposition. So, Je kiu koloro vi farbis la murojn

If we say Kiu koloro vi farbis la murojn, common sense tells us that the vi must be the subject of farbis, but the Kiu koloro induces the expectation that this is going to be the subject of an ensuing verb.

As Tempo succinctly put it: "Two nominative cases in a row ... this confuses me".

But the paradigms Mi farbis la murojn verdaj or Mi elektis lin Prezidanto tempt us towards the nominative.

On the other hand if we say Kiun koloron vi farbis la murojn, now we have what looks like two objects for farbis.

Neither two subjects, nor two objects is a good idea.

OK, you might be thinking at this point, enough of the linguistic waffle, you have presented us with a trivial problem with an easy solution.

However, in his translation of the Hound of the Baskervilles, no less an Esperantist than William Auld presents us with a sentence like Kio la homoj de la regiono nomas ĝin and just a few lines later a sentence like Ne atentu tion, kion la popolo nomas ĝin.

In these examples, a prepositional solution seems less obvious.

What are we to say about this? Pushing the boundaries of Esperanto syntax, or just another case, among many, of books being published in Esperanto without any proper editing first?

Side-note: Arie de Jong was apparently so irked by these constructions that he saw it necessary to add a special predicative case to Reform Volapük to avoid any possible ambiguity.

Kio la homoj de la regiono nomas ĝin

I don't like this at all. Why not Kiel la homoj de la regiono nomas ĝin? (assuming this was interrogative). After all, one asks: Kiel vi nomiĝas?

Ne atentu tion, kion la popolo nomas ĝin.

Similarly, why not: Ne atentu tion, kiel la popolo nomas ĝin. There is precedent for this combination of correlatives in the Tekstaro. (Parallel with Russian: Не обращайте внимание на то, как...)

Do i miss something or is this whole thread just about an English idiom?

Fenris_kcf:Do i miss something or is this whole thread just about an English idiom?

Yes, you've missed something. This thread is not about an English idiom, but about the question, whether or not it is possible in Esperanto to ask for a predicate noun.

nornen:
A: La disputo lacigas min.
B: Kio igas vin la disputo? [1]
A: Laca, tre laca.

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[1] This sentence is actually syntactically ambiguous, however semantically unambiguous. The question "What turned you into a discussion?" doesn't make any sense. At least outside of Disc World. But due to the double nominative, all sentences with a predicate noun are syntactically ambiguous in Eo. "La urbestro nomis la ratkapiston heroo." can be syntactically be interpreted as a) "The mayor called the rat-catcher a hero." or b) "Some hero called the rat-catcher the mayor (of this town)."

Why not "Kia igas vin la disputo?" since the answer is "laca"; an adjective.

"Kiaj vi farbis la murojn?" sounds weird to me, but might be grammatically acceptable for all I know.

"La urbestro nomis la ratkapiston heroo." can be syntactically be interpreted as a) "The mayor called the rat-catcher a hero." or b) "Some hero called the rat-catcher the mayor (of this town)."

But surely, the predicative usually comes second. This is one of the places where word order is crucial. Consider:

Glavoj iĝu plugiloj vs Plugiloj iĝu glavoj

Homoj estas bestoj vs Bestoj estas homoj

Two distinct meanings. There is no syntactic ambiguity - EO is simply forced to put the predicative second in most cases. It seems this also applies if you throw a direct object into the mix (like your example above).

Things get harder when you want to include interrogative correlatives as predicatives, since normally those correlatives want to sit at the beginning of the clause (constructions like ...tion, kion... are "fixed", forcing you into OVS or OSV for the clause introduced) - I think that's the core of the problem sudanglo wants to examine.

Christa627:Kia igas vin la disputo?

I like that. My first instinct was to put "kia" last, though - La disputo igas vin kia? ... Probably more influence from Russian.

Christa627:

nornen:
A: La disputo lacigas min.
B: Kio igas vin la disputo? [1]
A: Laca, tre laca.

----
[1] This sentence is actually syntactically ambiguous, however semantically unambiguous. The question "What turned you into a discussion?" doesn't make any sense. At least outside of Disc World. But due to the double nominative, all sentences with a predicate noun are syntactically ambiguous in Eo. "La urbestro nomis la ratkapiston heroo." can be syntactically be interpreted as a) "The mayor called the rat-catcher a hero." or b) "Some hero called the rat-catcher the mayor (of this town)."

Why not "Kia igas vin la disputo?" since the answer is "laca"; an adjective.

"Kiaj vi farbis la murojn?" sounds weird to me, but might be grammatically acceptable for all I know.

+1.

Yes Tempo, for the two offending Auld sentences, 'kiel' is satisfactory - so Kiel la homoj de la regio nomas ĝin?.

There is only a slight distinction between the manner of naming something and the choice of what something is called.

However, there is obviously a big distinction between kiel oni elektis lin prezidanto and enquiring as to what position he was chosen for.

Also, we find in Auld's Hound of the Baskervilles (that Dr Watson has been mistaken for Sir Henry is revealed) Kiu vi supozas lin? - which preserves the case usage of Mi supozis lin Kavaliro Henriko.

If this is OK, why is Kio oni nomas ĝin? unsettling?

Tempo:I think that's the core of the problem sudanglo wants to examine

Actually, my big issue is why Esperanto texts are not professionally edited before publication. But first, I wanted to establish that my lingvo-sento had not led me astray.

I think the issue are the two contradicting rules (never formulated, but obvious from the language use):
1. Wh-words come first.
2. Predicate (pro)nouns come after the subject. (adjectives are fine before, too)
So when a predicate (pro)noun has to appear as a wh-word, either one of the rules must be stronger than the other (appearantly for Auld 1. has priority) or the contradiction is solved by avoidance of such constructions.
The latter solution would be my choice, as both "Kiu vi supozas lin" and "Vi supozas lin kiu" sound bad to me.

Kirilo81:I think the issue are the two contradicting rules (never formulated, but obvious from the language use):
1. Wh-words come first.
2. Predicate (pro)nouns come after the subject. (adjectives are fine before, too)
So when a predicate (pro)noun has to appear as a wh-word, either one of the rules must be stronger than the other (appearantly for Auld 1. has priority) or the contradiction is solved by avoidance of such constructions.
The latter solution would be my choice, as both "Kiu vi supozas lin" and "Vi supozas lin kiu" sound bad to me.

Yes. This is what I was trying to express in my above post - but you said it better.

Wiliam Auld:Kiu vi supozas lin?

Still does not sound good. I would at least put kiu last, to preserve the normal word order (S-V-O-predicative). There is also the possible ambiguity of kiu being attached to vi - e.g., Kiu el vi?