Other features which can be used to differentiate adjectives from participles:
most adjectives have comparative and superlative forms,
most adjectives can be modified by adverbs of degree like very or absolutely , e.g. very rich or absolutely fabulous .

There are degrees of adjectivalness: the most adjectival adjectives have all four features: predicative use, attributive use, comparative and superlative forms, modifiable by adverbs of degree. Other adjectives may only have three of the features. Once we get down to only two or one of these features, the arguments start.

Bingley

Bingley