I understand what you are asking, and I admit, I have done this myself once or twice. I do not recall ever seeing anything explicitly forbidding it in eBay rules. I had an item that just wasn’t selling at the price I listed it at, for many weeks. Instead of cancelling it and listing it cheaper, I created another identical listing with a lower selling price. Interesting to note – the first item included free shipping, but the second cheaper price did not. The second item sold very soon thereafter, even though the total cost with shipping was higher!!
Technically it is not affecting or manipulating the search results. The search remains unaffected. What it is affecting is the buyer’s perception that one item is cheaper than all of the rest, so it must be a bargain. OTOH, if you would just list the cheaper price, they would not be paying anything more or less anyway. Many of the chinese sellers have multiple listings for the same items, varying the price by just one cent (look at button batteries for example). Their intention here is not price manipulation, but merely to get more ‘shelf space’ in the search results. It is like a cereal company having 40 flavors instead of two, just to hog more retail shelf space.
It is notable that most of eBay’s policies are primarily intended to protect their profits, not the sellers or buyers. So this practice would be very low on their priority to prevent, as long as they are getting their selling fees. In fact, the people doing it are often high-volume sellers, which are eBay’s best customers.