I read some stuff on the net, some vote completely against using WD-40 and claimed it's better leaving the chain dry, instead of using WD-40, but mostly it was said that WD-40 also contains a light lubricant which is good for light applications link hinges not bike chain, though it's better than leaving the chain dry, and some said it's not the best but good enough.

So, any way, you're right, but as long as the bike is working with out making any noise, i assume it's OK, don't know if it's a good judgment or not.