"Code smells". "Technical debt". These are the kind of things that engineers know about. Some amount is ok, but too much will shutdown a project -- even a company. EBay famously had so much technical debt that the company nearly shut down in the late 90s.

The next (and smart) question to ask is "How much is too much?" This is an area that I've always felt the tech community does a bad job of coming through on. Without being hands-on in a codebase, we haven't done a great job of offering coherent advice on the subject.

In a great writeup by Aiko Yamashita and Thomas Flemming, they dissect a few popular issues that developers bring up around code smells, and I think this is exactly what everyone needs.

(Note: some people have commented on the blog URL. Although the post is in English, the blog URL is Norwegian.)