Script Summary: Replaces poor spelling and grammar and capitalises the first letter of sentences. The core of the script is based on Rllmuk Tidy.
Reddit has its fair share of grammar Nazis, battling an endless flood of users writing could of, should of, alot and so on in comments. If you agree with them, then this is probably a script worth trying.
Running this using GreaseMonkey means that you don't have to read those mistakes, as they're replaced with the corrected text. Lowercase i is capitalised, america becomes America, and the first letter of every sentence is capitalised etc.
It's easy to add your own corrections too, although probably best to start by modifying the case insensitive section. I'll update this every so often with my current corrections so that it fixes as many issues as possible.
As per the source code, this is based on this script:
Further code development was done by monogram on Reddit and ax on stackoverflow.com
2009/12/15 Updated to stop it screwing up posted code and added some more corrections.