Thank you to Anh for sharing this useful grammar point with the Members Academy.
You probably know the 'rules' about comparisons:
SHORT adjectives: add '-er' (+ than), for example:
LONG adjectives: add more/less + adjective (+ than), for example
There are some ONE-SYLLABLE adjectives that use 'MORE + THAN':
1. one-syllable past participle adjectives such as bored, tired, pleased, worn
e.g. I'm more tired than I was yesterday.
2. with 'fun' 'real' 'right' and 'wrong'
e.g. It's more fun* to take part in sport than to watch it.
*some people say 'funner' and 'the funnest'
(examples from Murphy Grammar Book)