Comparing Communism to communism
According to the 1996 third edition of Fowler's Modern English Usage, communism and derived words are written with the lower case c except when they refer to a political party of that name, a member of that party, or a government led by such a party, in which case the word is written "Communist" (with an upper case C). Thus, one may be a communist (an advocate of communism) without being a Communist (a member of a Communist Party or another similar organization).
Other sources[attribution needed] do not back up this claim in the change of the English language as few follow this rule in academic or scholarly sources