There’s no hyphen between meta and http-equiv. They’re just overloading IE’s misguided quirksmode switch. As this is an IE plugin, I guess this decision won’t do much harm, because X-UA-Compatible is in IE anyway. An IE without the plugin will probably ignore this meta directive and use DOCTYPE to decide between quirks and standards mode, so maybe it’s even a good thing because it breaks the intended use of X-UA-Compatible.
Mozilla planned to do something similar with ScreamingMonkey, but by hooking <script type="application/ecmascript;version=4"> and <script type="application/javascript;version=2">, but that seems to have died with ActionMonkey.
Sigh, and your site has forgotten me again. Maybe a year isn’t long enough for a cookie, given the odds I’ll comment in the same browser in that time.