A better translation of 假作真时真亦假，无为有处有还无。 In the Chinese classic 红楼梦 ("Dream of Red Mansions"), there is a famous couplet:

假作真时真亦假，无为有处有还无。


Pinyin:

jiǎ zuò zhēn shí zhēn yì jiǎ, wú wéi yǒu chù yǒu huán wú.


This has been translated into English as:

Truth becomes fiction when the fiction's true;
Real becomes not-real where the unreal's real.


Another common translation:

When false is taken for true, true becomes false;
If non-being turns into being, being becomes non-being.


I find these translations at best stilted, and at worst nonsensical, and feel they lack the impact of the original. I'd like to propose an alternative translation, but as a non-native speaker I'm not sure how much of the original meaning I've lost.

My attempt:

When pretense receives credence, even honesty is faked;
Where vanity is given significance, significance becomes meaningless.


Is this a fair translation? Is there some shade of meaning in the original that this fails to convey which either of the two previous translations are able to capture? I would especially love to hear an answer from someone who considers themselves an expert on the novel (红学家).

Edit: I tweaked my translation of the first half and changed my translation of the last half:

When pretense receives credence, even honesty is mistrusted;
Where we pretend to have, what we have is lost.


Not sure if it's any better though.
One of the quotes you give is from David Hawkes, published, translation. It goes as follows:


  Truth becomes fiction when the fiction’s true;
  Real becomes not-real where the unreal’s real.


You can also consider H. Bencraft Joly's, older, published, translation of the sentence looks like this:


  When falsehood stands for truth, truth likewise becomes false,
  Where naught be made to aught, aught changes into naught.


Gladys Yang and Yang Xianyi's translation:


  When false is taken for true, true becomes false;
  If non-being turn into being, being becomes non-being.