There's a rumor (attributed to Shog9 but not verifiable by me) that
If six users without the ability to delete "recommend deletion", the post will also be automatically deleted.
If this is true, I find it worrisome. It creates a parallel vote-to-delete that users between 2000 and 20,000 rep can vote in, even if some of these users are not even trusted to vote to close.
What's more, these users are presented with the choice in a way that stongly encourages them to vote for deletion, in that the only alternatives (apart from "don't know") is "looks good" and "edit it to look good". This suggests to users that if they understand the question and the answer (and so "don't know" is not right), there is no middle ground between answers that "look good" (or can be made to do so) and answers that ought to be deleted. In effect the UI is suggesting that unless the user would upvote the answer, he should vote for deletion -- even though the vote is presented to him as a "recommendation".
It feels very backwards to encourage users to vote to delete by making it free, whereas merely downvoting an answer costs 1 rep.
At least at Math.SE we have a significant population of answers that are not good answers, but nevertheless shouldn't be deleted -- downvotes are the right way to deal with them. These answers are often short enough to trigger the low-quality filter. Their major characteristic is that they often embody the first instinctive reaction of somebody looking at the question, but are actually wrong for subtle reasons explained in comments or other answers. Having them stay visible but downvoted conveys valuable information to the reader, namely that this intuitively "obvious" answer is in fact wrong. Deleting them would entail a loss in usefulness.
If the secret parallel deletion vote is real, I think that
It should be made much more obvious to the user casting the "recommendation" that such a recommendation is in fact a vote that will cause automatic deletion without being reviewed by a moderator or high-rep user.
The review interface really should provide a middle way between "looks good, I will upvote" and "burn it with fire!", such as "no action is needed" or "downvoting is good enough for this".
suggest deleteshouldn't actually delete the post, but just put it in another queue for >20k rep users & dimonds to actually delete, or are you suggesting the UI be updated such that <20k users are not encouraged to make bad decisions (or both)?