Regarding _criticizing restaurants_, the relevant Wikivoyage policy is " "Avoid negative reviews"[1] which says:
"Sometimes a restaurant, bar, hotel, or other attraction has such grave defects that it's just not worth going to. If this is the case, it's best to just leave it out of the destination guide for the place it's in. There's no reason to clutter up a guide with lists of places travellers shouldn't go. "The exception to this rule, however, is when travellers may be led to the attraction by other information sources."
(See the policy for details.) This serves the overall Wikivoyage guideline that "The traveler comes first."
If need arises we could modify the "Avoid negative reviews" policy, but it has worked thus far.
The "See also" section of that policy links to the following four other policies that inform the tone of the policy:
Tone Be fair The traveller comes first Don't tout
[1] http://en.wikivoyage.org/wiki/Wikivoyage:Avoid_negative_reviews
Roger