[Question] What's the purpose of the "badfilter" directive, semantical-wise?

[MasterInQuestion]

    According to the documentation [ https://github.com/gorhill/uBlock/wiki/Static-filter-syntax#badfilter ], it appears to be much no more than... merely commenting?
    Which I suppose is already possible with /^!/m ("!" at start of line)?

[mapx-]

uBO is using not only its own lists.
If a wrong filter has been added to Easylist for example, you have a tool to nullify it, badfiltering it:

wrong filter:
||example.com/player.js

A uBO maintainer will add in this care (in unbreak list)
||example.com/player.js$badfilter

and the Easylist filter will cease to exist for uBO

[MasterInQuestion]

    So there's some other filter implementation that does not support commenting (or does not use "!" commenting)?
    Thus I assume "badfilter" directive is for compatibility ported from some other filter implementation?

[mapx-]

There is nothing about "commenting" in using badfilter

The wiki is very clear: To disable an existing filter

[gwarser]

So there's some other filter implementation that does not support commenting (or does not use "!" commenting)? Thus I assume "badfilter" directive is for compatibility ported from some other filter implementation?

You cannot "comment" in filter list maintained by someone else and downloaded from remote location.