JamesNK/Newtonsoft.Json — pull request #338 by bbowyersmyth (2014-07-29 10:05:47+00:00)
Title: Symbol chars used instead of single length strings

StartsWith(char) and EndsWith(char) extension methods are twice as fast as the string based versions.
StringBuilder.Append(char) is a direct assignment to it's internal buffer and doesn't setup a memory copy operation.
TextWriter.Write(char) is the same as the StringBuilder. Typically a direct assignment to an internal buffer.