If you want "Find in files..." to only show // style comments, you can use the regular expression
//.*SearchTerm
However, "Find in files..." only deals with single lines, so using a regex (ex. /\*(.|[\r\n])*?\*/) for multi-line /* */ style comments is impossible.
If you plan to make a patch (:)), I have been messing around with syntax highlighting recently. The following are some useful things I discovered in relation to this (if you need a place to start).
#include <cbstyledtextctrl.h>
[...]
int posOfSearchTerm = pos;
cbEditor* ed = Manager::Get()->GetEditorManager()->GetBuiltinActiveEditor();
cbStyledTextCtrl* control = ed->GetControl();
[...]
myColoringFunction(control->GetStyleAt(posOfSearchTerm));
src/sdk/resources/lexers/lexer_cpp.xml (http://svn.berlios.de/wsvn/codeblocks/trunk/src/sdk/resources/lexers/lexer_cpp.xml)
src/sdk/wxscintilla/include/wx/wxscintilla.h (http://svn.berlios.de/wsvn/codeblocks/trunk/src/sdk/wxscintilla/include/wx/wxscintilla.h)