I think I hit a tiny bug.
Specs:
Code::Blocks svn9616 (32-bit)
wxMSW-2.8.12 (32-bit)
TDM's GCC 4.8.1 (32-bit)
Windows 7 Enterprise 64-bit
Issue: I insert a string without double quotes, I highlight it, and then press shift-double quote and adds an extra double quote.
Before:
After: