Thanks Arpi, tumhari sangat ka asar hai
If I had to differentiate between the two words, I'd say that inspired for me is wanting to become a super power but over inspired is when I nuke the world for it and not apologise.
Also it's a prejudicial notion too. If you are a beginner, lesser known photoshoper and you get inspired you'll be called out in a not so nice manner but if you are established, you'll have the benefit of doubt in your favour because as someone who has achieved the PSer fame people would avoid your glitch becuase they would think you don't need to be "inspired" and the result is just a coincidence.
Thus a newbie gets the tag of over inspired and an oldie loses nothing much most of the time and passes by as "might have got a bit inspired."
At the end a moral fibre helps everyone. You'd know if you got inspired or not so just put a credit up. With practice and patience you'll achieve the status quo and understand why people get touchy with these words.