I agree with other responses to this comment. Ugliness might have had a reason, ok. It's important to understand that. The question is whether it has a reason to stay. And here we find the usual balance between the effort it takes to maintain ugly code and the effort it takes writing new one. On another point... I understand calling that "accumulated knowledge". But that's knowledge accumulated very badly. You want to accumulate knowledge? Write tests when needed, comment them when needed, add comments when needed in the comment. That's accumulated knowedge too, and you are actually making it way easier to transfer, which is definitely one of the most important parts. If you were already doing things right, that's another story, but in general, if you look at code and your brain goes "what the..? no, please, why did you... T_T", there's probably a need for a rewrite.

EDIT: I think it's also important to mention the value in rewrites, specially on your own code. Spend a lot of time thinking how to make your code simpler, easier to follow, cleaner. That will help you write much better code in the future. A lot of people would benefit from this if they tried. Writing code that works is simple, writing good code is very hard. And rewriting code teaches a lot of the second. When you are learning, rewrite a lot. When you think you know what you are doing but someone suggests to rewrite (and you know they are good programmers too), at least listen.