This post is a reply of sorts to the two excellent points raised in the comment to the previous post. You will need to read the brief comment to get the context here.
The range of language (even just in vocabulary) available to Ghalib is in fact the striking thing here. I am quite ignorant of English poetry in general but it seems to me that there isn't anything quite like this there. Poetic language can be simple or complex in different English poems, but words are generally not used verbatim (tatsam) from say German or French, except in unusual circumstances. While in Urdu, tatsam and tadbhav words can certainly be used from Sanksrit, and to extend the usage of tatsam and tadbhav, such words can also be used from Persian and Arabic (less frequently than Persian).
The manner of speaking a language is often associated with social class (this relates to the second point regarding the intended audience of a particular poem). As pointed out the vocabulary of different classes may have been vastly different during Ghalib's time. At least literary vocabulary was much more Persianized than street tongue. This harks back to the distinction between Sanskrit as the language of literature and the various Prakrits or Pali as the language of ordinary discourse.
Of course this class distinction also provokes literature in the ordinary tongue (like the Buddhist canon in Pali, instead of Sanskrit) as an explicit effort to make literature accessible to the ordinary person.
With a assuredly class conscious person like Ghalib, one wonders what made him write in more accessible language at all. Perhaps he felt a tension between composing in "high language" and the popularity to be gained by composing in "low language".
Also I suspect that he would have made a clear distinction between high and low language and high and low quality. As we know his simple and complex verses are both brilliant. So he really shows in some sense that language doesn't matter. He can be good at it all.
The one last thing to say is that he is reported to have said that all his Urdu divan is as naught compared to his Persian verse. But I don't know how much to believe that. After all he also says:
jo kehe ye ki rekhta kyun ke ho rashk-e-farsi
gufta-e-ghalib ek bar use padh ke suna, ke yun
To the one who says "how can Rekhta (Urdu) be the envy of Persian
Show him Ghalib's verse just once, and say "like so"!