has cold fusion really been discovered?

The short answer is no.

In science, it is important that results be repeatable. This is especially true when dealing with some phenomenon like cold fusion which appears to violate all the principles that we understand.

Pons and Fleishman and others tried to reproduce the observations, and were unable to do so reliably. A recent review by the Department of Energy of 15 years of research and efforts in the field reached the conclusion that this phenomenon does not exist, or at least cannot be verified.

At this point, the accepted answer appears to be No.

There are still a number of people and organizations researching cold fusion. Some of these are well-known and well-respected. So, why do research in an area that looks to be useless?

Cold fusion was claimed because the energy output from the experiment was greater than the energy imput. BUT, the differences are so tiny that they're on the very edge of measurability and generally within the bounds of variability between experiments. In other words, it's hard to see that it's even there. Some experimenters get the effect, some don't. And no government or energy company wants wants to be the last to figure out that there's big dollars or military applications in some strange particle interaction in a testube that they weren't aware of.

No one wanted to let this go because there's always the chance that there really is something there, but it's so small that it's useless. Or there's something there, and we can really make use of it with some specific design. Or, there's no cold fusion, but there is something else interesting going on that we can use, and cold fusion experiemnts allow us to find out about that other mechanism.

The popular idea of sticking a couple of wires in a test tube on a desk and lighting 1,000 lightbulbs continuously for the next 100 years just isn't going to happen. People still want to look for other effects that may be important .

In the cold fusion process, particles that are only normally seen during nuclear reactions were measured to have been produced by the experiment.

However, the results are considered to have been improperly measured and invalid.

In other words, cold fusion does not exist.

It's a programming language.