Steps to reproduce:

1. Install Confluence
2. Navigate to Administrations > Layout > click on Create Custom option for the "Classic Comments Layout"

Expected Behaviour

Confluence shows

Actual Behaviour

Confluence throws A decorator was requested that odoes not exist: decorators/components/sharedcomments.vmd

Workaround

1. Create empty file <confluence_install/confluence/decorators/components/sharedcomments.vmd
2. Navigate back to Administrations > Layout > click on Create Custom option for the "Classic Comments Layout"