how to create single spreadsheet with user specific access to tabs

sorenrahr  you would need to use VBA to perform that sort of actions.  You would check on load/opening for the user name and/or provide a login box and then show only the corresponding tab.  As for comments vs. edits if the built in sheet/workbook protection can't be configured accordingly then VBA would be used for that also.

  The Problem is that VBA doesn't run in the online version!  So IF you are to move forward, you could do all that but the users wouldn't see anything unless they open it in their desktop version (click the little button that says open in app).  

  Alternatively, you could create a new spreadsheet for each user that pulls data from the master and has permission rights only allowing the corresponding user to open/view.  As for comments i would just lock the cells with values in them and give the user a column or 2 open for comments.