johnblack - 8:55 am on Oct 6, 2010 (gmt 0)
I'm sorry I've not read through all the comments, so apologies if I'm repeating things someone has already said.
If I were in your shoes I'd wonder why he wrote the code the way he did. You can even ask him if you want, I don't think it would be rude especially if you are expected to pick it up soon. There may be valid reasons why he did it the way he did. Time constraints, design restrictions imposed by others, or he just did not think of it at the time.
I've sometimes looked at old code that I've been handed to debug and my first reaction is why on earth did the developer write it this way. Then on deeper inspection I've spotted my own name in the comments section of the code!
Do you have coding standards in place? Do you have peer code reviews? Both I think are good ideas and probably necessary in multi-developer environments. I'll be saying developers should write documentation next ;-)
Anyway tread carefully, but if you're expected to pick up this code, I don't see any problem in politely asking why it's been written the way it has.