I think the term over-optimization is misleading and may be the cause of this confusion.
For me, using the same keyword in anchor text of links is actually not over-optimization, it is rather under-optimization.
If you have the ability to control the anchor texts and don't utilize it to diversify, you are losing a great chance of optimizing a page for other key words. You are making it less competitive.
Less competitive pages are the type of pages you find in many article farms.
In Wordpress, the issue of internal links as I described above is so extensive that if one doesn't have some php knowledge (and SEO skills), it can't be fixed.
Again, this is my way of working on my sites. I have never sold SEO services to anyone.