2 step workflow: How does a user such as John see the comments from the previous user asking for some changes + restart the complex workflow?

Initiated a complex workflow with John. Then a Validator asked for some corrections + entered some comments. Once into the correction mode, John can perform some changes on this page (lock are not present any more). But:

• how does John can read and access to the comments/feedacks from the previous user(s)? Wouldn't it be more simple to display a "discussion thread" icon in the workflow dashboard if there is a discussion thread available?
• Once the correction finished, how can John restart the current workflow. There is no option to access the workflow engine from the worfklow dashboard.