When is authentic too authentic?

Budget supermarket chain Lidl decided to crowd-source its advertising via customer tweets.  Not a bad idea, but my photo reveals that not all people are copy editors.

Would correcting the grammar have undermined the authenticity? Does reproducing the error suggest a lack of attention to detail and reflect badly on the brand? It's a judgment call.

Lidl apparently decided it's OK to leave the comment to stand on its own merits. Or did they?