:Hi Mokhov.  As the article states, "moonlet" is an informal term, and as such I would discourage its use.  Generally, people call something a "moonlet" because they see it as small and cute, but in that case why not use the more precise term "moon"?   
 :Precision in language is important, especially in an encyclopedia.  You may have heard that there has been controversy regarding the definition of "planet".  Well, if the word "moonlet" becomes more widely used, eventually there may have to be some wrangling over the difference between a "moon" and a "moonlet".  Whatever the conclusion of such a discussion would be (I have my opinions, but won't discuss them here), it certainly will not be that we should call something a "moonlet" simply because it is small and cute.  
 :Regarding your last question, I am sure that you are very well-read in astronomy, but Wikipedia relies on not the opinions of editors like you or me but on reliable sources.  As I've said, I would discourage the use of the word "moonlet" in many cases, at least those for which "moon" would do just as well.  But when a reliable source uses the word, then it is appropriate for WP to make note of the fact.   /