Bing has confirmed that click through rate (CTR) is one of many factors in their ranking algorithm. Steve Tullis, Senior Program Manager Lead, Bing, said at SMX that if pages in the search results don't get clicked on, the ranking will likely be lower.
The following text highlights differences in how keyword duplication is treated, and using Microsoft Advertising Intelligence to fine-tune your keyword roster. "Keyword normalization is a process by which a paid search provider finds and flags duplicate keywords within an ad group. This process occurs automatically, and usually saves you time, because you don't have to manage multiple variations of same keyword. YSM used a keyword mapping system in which singular and plural variations, and common misspellings of a keyword, map to primary form of that keyword. The net result is that you don't need to bid on multiple variations of a keyword," explained Yahoo!.
A keyword is considered duplicate by adCenter if it contains extraneous characters or words, or if its punctuation or capitalization are slightly different. So if you want to receive traffic from them, you'll have to add each variation to your campaigns. When you import keyword list, duplicate keywords within same ad group will be flagged with an error message and not uploaded in adCenter. This gives you a chance to review the list and make any necessary edits.