User mention can't be added into inline comment

Bug Summary:

User Mention can't be added into inline comment

Environment:

Confluence 6.6.1 (Linux 64bit), Google Chrome 63, Database: PostgreSQL 9.4

Steps to replicate

1. Add PDF or doc attachment to any page, save the page
2. Click on newly added attachment to display attachment preview, add inline comment
3. Within incline comment text entry box add any existing user by using mention feature and some text.

Expected results

Inline comment will be added to attachment and user should receive one email notification due to the mention

Actual results

Created Inline comment with user mention doesn't contain any content.

Workaround

• Unknown