I have an easy rule: Always start with a honest "Awesome, ...".
"Awesome, your code is very readable."
"Awesome, your layout is great."
"Awesome, your site looks great."
What if it's not?
I think there's always one small thing.
"Awesome, you put some hard effort into it."
I appreciate your sarcasm :)
(in case it was not - read below)
I had two colleagues, who used to make me scream when seeing their code. First was so completely incompetent, that whatever he touched made significant regress, but he tried hard. Damn hard. He used to work for 10h/day and read tutorials for another few in his free time, but still 1 year and a half later he produced such unimaginable things, that I had to delete 80% of his code (and usually replace 10 lines with a single statement if at all).
The other one was competent, but sort of lazy and usually handed me code, where 60% of it was commented tests, some was incomplete and poorly tested. When asked to clean up his code he usually deleted the commented code... and a few lines of non-commented code inside them (yeah one can hardly spot them sometimes) and didn't even test before marking the task as complete.
The first person is usually the type of person that I PERSONALLY will take time out of my day to sit next to and help out. Maybe code review the stuff together. I find that helps me fully get their thought process and I can explain my thought process more verbally and not just written. I personally have helped a few people that fit what you described (and I think more people who code review should do it).
The 2nd person should be brought up with to upper management in my mind. That's not fulfilling your job duties and his hurting the project and the company in the long run.
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