Are you using comments for fields or comments for the views? Some options.
You can add comments for fields in Desktop and these will persist on Tableau Server. Use the function "Default Properties" from the Drop down menu of a field in the Dimensions/Measures pane. The option 'Comment" appears and it is here that you can document the field information desired.
Next, you can utilize worksheet Captions from the Worksheet menu . This is a great location to describe what a specific sheet does.
For dashboards, you could utilize a text dashboard element right in a dashboard to describe and comment on a dashboard.
Finally, you could utilize annotations within a view to describe specific areas or marks in the views.
I hope that help.
We recently released an extension to help with the commenting issue called Steward. It allows you to leave comments on specific marks. The comment and associated metadata gets sent to a central queue where people can view and collaborate on the issue. You can grab it free from the Extension Gallery
Hope that helps.