Cold fusion, to my knowledge, is and should not be treated differently than any other topic on the "fringe" of mainstream science.
In general, questions about non-mainstream science are off-topic. It should be stressed that this does not imply that non-mainstream theories are entirely without merit (though they very often are), it merely says that we as a community do not want to have such debates on this site, as they are contrary to the Q&A formula of SE sites where it is expected that question have at least one correct answer based in currently accepeted expertise.
So, for example, asking whether X is possible within currently accepted physical theories, or what things forbid X from happening is on-topic. Presenting your own personal theory about X and asking for comments is off-topic, as well as questions asked in bad faith where it is evident that the asker will just keep moving the goalposts so that no answer is ever satisfactory, as well as questions of the kind "Isn't physics wrong about X?" or similar.
It doesn't matter what kind of "non-mainstream" science X is here.