"I believe the difference is, with Reggae/Ragga/Ska/Rocksteady or with Rap/Hip-Hop people are generally using the definitions to describe songs and styles and convey to somebody how something sounds. I think this is a good reason for having definitions and knowing what different musical styles are called.

HOWEVER, it seems to me that on this forum, the only reason people ever want to define 'folk' is to decide which acts can be excluded from the genre, as opposed to helping to describe/define different styles or preferences within the genre."

The author of the above quote seems to be suggesting that it's OK to use definitions, and different shades of meaning, to differentiate between 'different' types of popular music but it's NOT OK to apply such distinctions to Folk. I have always suspected that this attitude stems from an underlying belief that Folk Music is really 'just' another form of Pop music (in the late Twentieth Century/early Twenty First Century sense) and 'should' be more like those forms of Pop music. People seem to be mysteriously outraged that Folk doesn't conform to their preconceptions and start throwing accusations of compulsion and exclusion around. Folk just isn't the same (which is one of the reasons why I am interested in it) - get over it and get on with making what ever type of music you like - I'm not stopping you! If you're so desperate for the approval of pedants like me, and a handfull of others on this board, you must be lacking in self-belief - that's all I can think ...

And, yet again, seeking to define something has nothing to do with preference - how many more times?