@Grey Wolf
'I cannot praise X highly enough.' (i.e. I would if I could, but I cannot)
'The contributions X has made to our team are incalculable.' (and, perhaps, infinitesimal - or imaginary)
I would actually disagree. It could be a localisation/regional thing, or even a contextual one, where the meaning is decided by tone of voice or facial expression. Both of those examples I have found to be generally used in a positive light in the UK. Very rarely, with heavy sarcasm, I have heard "I cannot praise (them) highly enough" used amongst people where the individual in question is known to the other(s) in the conversation as being a complete 'tool'.
Any dialogue that requires extensive body language to be correctly understood, I would avoid using in a story, as the need for that to be conveyed to the reader would harm the story. And to be honest, the technical ability to carry it off well, is far beyond that of the average writer on this site.