I also find it distracting because it suggests inaccessibility - and the lock icon is being used with two different meanings: for closed topics and for “private” i.e. “non public” categories which is confusing. So confusing and distracting: not good.
The categories that are not public that you cannot access are invisible, so they don’t need an icon.
So the icon for a non-public category that you can access should indicate two things:
- you have access to it
- other people might not
So how about… 
