OSFMount volumes not really read-only?

[Haxor]

I upgraded an HDD and I used dd to make a raw image of it (as we know, file-level copies often fail and are slow). Today, I encountered a very weird bug. Not remembering that I mounted the image as read-only, I zipped (by 'send to..') bunch of files and it succeeded. Wait, what? The volume was supposed to be read-only. Modification date for the image hasn't changed, though.
What is going on here?
I used version 1.5 (build 1015)., Win8.1 x64

[keith]

What is the file system in the image?

We tried to reproduce with NTFS and FAT raw images but got the error message:
"File not found or no read permission"

Can you post a screenshot of the problem.