[mod-security-users] Proxy issue "Not Acceptable"

[<030...@mu...>]

I write not as a user of Mod-Security, but as a victim. As a web surfer 
in the Paranoid++ category, I am encountering an increasing number of 
senseless roadblocks on blog sites due to my security configuration, 
none of them giving me specific information about what's gone wrong. I 
want to know what I can do about it.

As of late, when browsing the web, I have been running into an 
increasing number of denials in this form:

---
Not Acceptable!

An appropriate representation of the requested resource could not be 
found on this server. This error was generated by Mod_Security.
---

I figure that this is about 79% due to mod_sec setups that are poorly or 
entirely unconfigured, and 19% due to my extremely conservative proxy 
config. I browse with a local (admittedly old) Internet Junkbuster 
proxy, and relay through my ISP's Privoxy/Squid setup. I want to find 
out what this setup is doing to trigger these Not Acceptable responses, 
and what I can do to fix it.