This is something like curiosity, even though I always advise clients to close the app properly.

What will happen to a DE8 database, if a user shuts down the workstation without properly closing the DE8 app.
And a form was open at the time of shutting down. 

Will this create any issues with RDRR file?

Will it create any issues with index files?

There is a big distance between what people should do and what they actually do.

This is a little like not using a Mobile on a plane. If it was really true that a plane would fall out of the air if someone forgot to switch off their phone or received/made a call we would all be dead by now. That said it doesn't mean that in a freak combination of events it couldn't happen...

DataEase would never work if it would corrupt data every time people stopped an app in the wrong way. 

However there is combinations that would it more likely to create corruption. 

A*) Biggest difference is locking model. If you use Basic or Full you are 10-100 times as likely to get corruption in these instances compared to Opportunistic.
1) If a DQL is "hanging" and the user decide to Kill DE or Reboot WorkStation. With Full or Basic this will almost guarantee corruption.
2) With Full locking and the User has been viewing/editing the a form.

As you see the locking model is the main culprit, but the server settings with OpLock and Caching etc will contribute to.