Yes, it can inflict more harm by forcing you into suboptimal decisions. Shame can be alike too. So, I vote for insect-like shame and pain processing, I've mentioned in grandparent.
There are cases of people with no sense of pain. Here's an article about it:
http://findarticles.com/p/articles/mi_m1200/is_25_170/ai_n26713199/
...and a link to the primary it references, if you have a subscription to Nature:
http://www.nature.com/nature/journal/v444/n7121/full/nature05413.html
A relevant quote from the review:
"The team's first research subject, a 10-year-old boy, was well known in his community for street performances in which he placed knives through his arms and walked on hot coals. Despite tissue damage, he apparently felt no discomf...
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.