my present specific area is adult L2 acquisition and i have done work earlier on prosody, codeswitching, bilingualism, phonetics, language typology, sign language, space, language & cognition, L1 attrition and pidgins/creole languages.
i consider myself expert enough to have an opinion on what is a language and what is a dialect.
i do not have a high opinion of the "fuzzy chinese" article by the way, for several reasons.