Duplicating and renaming files from acorn - not quite right?

I find that when I create a copy of a file from Acorn - as I have just done using the Duplicate File menu option - the new file name isn’t what I expect it to be:

What happens
The new file appears to be called filename.acorn copy when it appears. However when save the Save As… field offers me filename.acorn copy.acorn. As my filename may already be long I often don’t see the end of the field and just accept.

What I expect
I expect the new filename to appear as filename copy, and to be saved as filename copy.acorn. (Assuming I accept the filename field as is.

I am running Acorn Version 6.3.3 (13438) on OS X El Capitan 10.11.6

New imac soon to be ordered. Mine is a 2009 machine, so it has served me very, very well but it does struggle sometimes.

Perhaps you could get used to using cmd-shift-S “Save As…”, rather than “Duplicate”. It will force you to manually alter the filename, or approve overwriting the original.

Yes, I do that - as I have learned to do with preview before I touch anything!

However, in this case I would classify the naming of the copy as a bug, rather than an inconvenience.

I will work around it, but it is not the way one expects it to work.

I consider this a bug as well. I can get it to reproduce on 10.14 + Acorn 6. I’ll get it fixed (though, maybe not tomorrow…)