In Toad 9.5 even if I check View | Toad Options | Data Grids | Data | "User read-only query," I can still do the following.
1. Add and delete rows. Notice that the + and - sign in the Schema Browser | Table | Data is still lit up.
2. Edit data by going through the Single Record View.
This issue is also not observed in Toad 9.0.1 or 9.1.
This issue is resolved so far in the Toad 9.6
The latest version of Toad for Oracle can be downloaded at the Support Portal.