このことばは、何のいみですか? Is this an invalid way of asking?
It's valid. Alternatively you can use '...どういう意味ですか?'.
どういう意味ですか is definitely more common.
I tried the same, pretty sure it's valid but just hasn't been added yet.
Still not accepted.
As the question is phrased that is a better translation. 「この言葉の意味は何ですか」is a better translating for "What is the meaning of this word."
why does this not work?
Apparently (and ironically) Duo has a hard time accepting answers with kanji in them.
Duolingo is incoherent: sometimes it accepts kanji, sometimes not, sometimes in only half of the sentence ...
この言葉のいみは何ですか was rejected as well as この言葉の意味は何ですか. Seriously Duo?!
この言葉のいみは何ですか was not accepted. I reported and hope that they fixes that soon. I`m trying to get used to using kanji in all phrases here. And just knew that I can use 意味 instead as いみ as well, looking at some commentaries.