... is a community whose members help each other develop better code by providing feedback through ratings, and whose structure facilitates the pairing of compatible managers and developers.
The issue with your sentence as originally written is that "a community" serves as sort of an anchor in the mind of the reader. Until another noun is used to act as another subject to be targeted by a pronoun, "a community" will be the subject. With that in mind, the issue is that "a community" is not what provides ratings in this case, but rather members within that community provide ratings. Further, "a community" would not likely pair members within itself, but the community existing and being structured in an effective way could ease the pairing of managers with developers. The use of "community" is reinforced by a second use of "whose" after "and", which reminds the reader that the members are not the focus of the sentence, but are instead an aspect of that focus.
The issue of sentences feeling awkward can often be solved by separating a compound sentence into its component parts, as you did originally, but you used a pronoun (it) in the second sentence rather than remind the reader of the community.