why community post doesn't support heic image, which shotted by iphone?

One additional possible reason; HEIC offers better compression, it is not natively supported by most web browsers or platforms, leading to compatibility issues.

Apple moderators do not respond here, just other end users. An email contact for them is posted several times itneh Terms of use we all signed:

Apple Support Community Terms of Use

I feel Bob has a good point when you consider the cross-browser compatibility issues that web developers face. Note in Settings > Camera > Formats, Apple calls the alternative imaging format "Most Compatible."

cruvie wrote:

why community post doesn't support heic image, which shotted by iphone?

Apple runs a tight ship, especially on divisions like support that don't generate revenue. Apple Support simply doesn't have the resources to keep up with developments from the rest of Apple.