People, when they mean nt as "No Text" on perhaps a message board, usually surround it with -'s, as: -NT-, or some other symbols. When you do this, you have a subject
with no text in the article it links to.
For instance on everything
, although this never happens
This is a nodeshell needs no writeup -NT-
And the author makes no writeup for his nodeshell, or merely puts the words "nt" in it, to signify that he has nothing further to say beyond the title of the nodeshell.
Some people use -NT- in normal conversation on IRC or ICQ. For instance when bragging or making the claim that their position is the end all to the conversation or situation.
"TX GG NT" is commonly used on FICS when someone wins a game. (Almost as much as "TX GG NP"
In conclusion, -NT- is used to make a short statement which defines how the author feels in dramatic fashion.