Is putting "for a moment" between subject and verb grammatical?

The Da Vinci Code isn't the most poorly written work of fiction I've ever read, but so very close. However, who am I to argue with success? From Dan Brown's own website: http://www.danbrown.com/#author-section

As Edwin Ashworth and WS2 stated:

"I'd say it's towards the 'reject' end of the acceptability scale. Most adverbs have a very free distribution, but not a totally free one. Longer adverbials are, I'd say, less freely distributed. These Google Ngrams, and raw Google search results, would seem to indicate preferred usage."

and,

"[It's] more idiomatic to say For a moment, he looked as if he'd seen a ghost and keep both parts of the verb together. If in doubt,my own rule is to keep the verb parts (person and verb itself) together."