The Plugin method, OpenScript(scriptInstance [, lineNumber]) does not open ModuleScripts. No errors are shown. If you try to open up a non-script object (such as a Model) you get an error. Therefore, I assume it is supposed to work on ModuleScripts. Nothing happens though.
Easy to repro. Just use a plugin and try it on Scripts, LocalScripts, ModuleScripts, and non-scripts. Scripts and LocalScripts work, ModuleScripts do not.