For example, should we make sure all instances of "sulphur hexafluoride" are all lowercase, all first case ("Sulphur Hexafluoride"), or just leave it however the author wrote it?
I'm going to say we should not capitalize the full names; per Wikipedia:
In former versions of the IUPAC recommendations, names were written with a capital initial letter. This practice has been abandoned in later publications. The names of chemical compounds and chemical elements when written out, are common nouns in English, rather than proper nouns. They are capitalized at the beginning of a sentence or title, but not elsewhere.
Elements and formulas (He, NO2, ...) should, of course, adhere to the proper capitalization.
However, I would also suggest that having a capitalized name or two is not alone sufficient reason to edit a post, but if you are editing it anyway, do normalize the capitalization.
I think that capitalization isn't a big problem because the site's search function will find any form of the same words.
More importantly, we should probably standardize between American and British spelling (sulphur vs sulfur) so that one search finds all of the relevant questions/answers.