With that said...
I just finished reading through a messy Java file. It was the usual mess of a class with a 500 line god-method (similar to the god-object) and hundreds of counts of copy and pasted code. Besides the redundant code and lack of structure the coder also used nested loops through ArrayLists when they could have used a HashSet and didn't once use generic collections, using the un-type checked versions instead. After several hours of refactoring and renaming variables I finally got to a point where I could begin fixing the bug I was after. There were absolutely no unit tests - all this code was written inline with HTML in a JSP.
I spend so much time reading bad code that sometimes I wonder if I am beginning to specialize in hacks. Is it possible to read so much bad code that you forget what good code looks like? Humans are an especially adaptive species, and I think it's definitely possible that a great programmer can be forced to work in the muck so long that they forget what good code looks like.
I've seen several situations where good developers produced bad code. These situations are almost always a product of an environment where features are more important than bug fixes. These companies typically invest heavily in sales and neglect IT and development costs. Or sometimes the problem is just that product management knows nothing of software development.
The 5 stages of grief
A recent coworker likened our job of working with brittle, badly designed code to the 5 stages of grief. While we were uneasily laughing about it I silently decided that this was more realistic than I wanted to believe.
For instance, imagine starting a new job. In the interview process you were interviewed by intelligent, enthusiastic developers and were led to believe you were going to be working on cutting edge technologies - a dream right? When you actually get to the job you find out that the code is so backwardly complicated that its nearly impossible to touch anything without bringing the proverbial house of cards crashing down.
Grief Stage 1: Denial and Isolation
Obviously the code isn't the problem, you just weren't careful enough. They probably have specific guidelines and strategies that help them be more productive. It's probably just something wrong with me...
Grief Stage 2: Anger
Dammit! Who the hell even thinks of this crap? [more cursing...] Is this a god-object?? [hair gets thinner...]
Grief Stage 3: Bargaining
This is typically when you start plotting potential strategies to hide the ugliness of the code. Creativity and hopeful thoughts abound. Many IT managers will talk like they are very supportive of you at this stage.
Grief Stage 4: Depression
This is where the reality strikes that this stage is bad for the business plan because it involves spending less time on revenue-producing features. The IT managers that seemed so supportive now flip flop to the CEO's side and deny you the ability to cope with your problems
Grief Stage 5: Acceptance
There are only two outcomes of this stage. Either (1) you accept that you can never fix the code so you decide to move on to another job or (2) you accept that you can never fix the code so you give up on trying. This is what separates good coders from bad.
Conclusion
Again, I started this post over a year ago. I've seen a lot of bad code. At my most recent job I almost took the "give up on trying" path in the acceptance stage. Luckily we hired a great older developer who snapped me out of it. I just started my new job today, I think I will be much happier.
So can bad code ruin your career? My answer is a resounding YES! But it doesn't have to. Honestly, stage 5 can have better endings, but that inevitably requires understanding on behalf of management - a scarce resource.