configure your vim to make that file with jsonc filetype to allow comment. code example
Example: coc allow comments in json
The filetype need to be jsonc.
To make Vim treat all json files as jsonc:
```
augroup JsonToJsonc
autocmd! FileType json set filetype=jsonc
augroup END
```
Or you can use a modeline (:help modeline) at the very top or bottom of an individual json file, to set the filetype to jsonc for only that file:
// vim: ft=jsonc