You can walk through pistons.
What I expected to happen was...:
I wouldn't be able to walk through pistons.
What actually happened was...:
I did walk through the piston
Steps to Reproduce:
When there is an extended piston you can walk through the line that connects the piston.
Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-3004. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.