Here's how to add and view comments on Skills:
Using the left side navigation menu, scroll to your organisation's name, then hit 'Skills'
You'll see a list of all the Skills currently used by your organisation
Find the Skill you want to view or add comments to and click the ellipsis '...' menu
When the Skill has expanded, click the ellipsis '...' menu and click 'Comments'
From here you can view and add comments on the Skill, and invite others to add and view comments.