Non-finished, blocked stories

The Sprint Goal is the commitment. What can the Developers do to ensure they meet it, even without the stakeholder feedback on particular stories which you describe?

You are not addressing the actual issue with any of your suggested solutions.  If the reason you cannot complete an item in your Sprint Backlog is because the stakeholders are not providing feedback, that is what you should address.  Why are they not able to provide the feedback?  Are they truly aware that their feedback is needed?  What mechanisms are you providing them to give you feedback?  Why is the feedback not being provided in the Sprint Review since that is one of the reasons for the Sprint Review? As a Developer on a Scrum Team, you should understand that this is a group decision as a Scrum Team is self-organizing, self-managing.  There is no one on person that makes this kind of decision.

To me, it sounds like you are suggesting ways to penalize someone because the Scrum Team is not doing their job of including the stakeholders in the process.  If you do that properly, stakeholder feedback is continuous and should rarely, if ever, result in the situation you are describing. What has your Product Owner and Scrum Master suggested in this case?  After all, the Product Owner is responsible for the management of the Product Backlog.  The Sprint Backlog is really just a subset of the Product Backlog that contains items that are currently being worked on by the Developers.  So, how does the Product Owner feel like this should/could be handled? What do the other Developers think about the situation?  Why is email the only mechanism available to interact with the stakeholders?    

To build on @Ian's response, are these items critical to the completion of the Sprint Goal?  If so, why has the need for stakeholder feedback not come up in the Daily Scrum where the Developers plan discuss their needs and activities for that day? 

blocked by stakeholders not providing necessary feedback

Are you able to elaborate on this a bit more? What stakeholder feedback blocks the team from building an increment or achieving their Sprint Goal? Is there a Product Owner in this scenario?

Two things that haavne't been mentioned yet that seem key to me are; Refinement and Definition of Done



Does your team have a definition of done? what does it include? 



If the team is unable to finish work because stakeholder feedback is required, it sounds like there are activities that should be captured in the DoD that we're not accounting for. 



At refinement and Planning sessions, we should be considering these activities and ensuring we've done the work required to ensure the work CAN be completed before we pull it in to a sprint. 



The simplest solution I've had with a team in a similar situation is to have that conversation at or just before sprint planning, and have the stakeholder commit to be available to provide their feedback before we will plan any work. If they cannot do that, we cannot start. 



The longer term question others have alluded to is 'why is the team so dependent on people outside the team' and what are they doing to resolve it? 



This smells to me a little like 'We've emailed someone and they haven't responded so the work is blocked'. The question Ian and Daniel raise is the right one. What is the team doing to unblock it? 



In the short term, I would suggest thinking about DoD and refinement, but longer term, Ian and Daniel are pointing you in the right direction.