Yeah, sorry. I made the comment right after I got back from my model logic class, so I was thinking in sentence letters and logical connectors.

For me this is the key passage in your post:

In fact, "I thought I wouldn't want to do/experience X, but upon trying it out I realized I was wrong" doesn't make sense. Previously the person didn't want X, but after trying it out they did want X. X has caused a change in their preferences by altering their brain. This doesn't mean that the pre-X person was wrong, it just means the post-X person has been changed. With the correct technology, anyone can be changed to prefer anything.

This effectively shows that the claim "I desire X", when made right now can't be falsified by any desires I might have at different times. I actually don't think this a point about technology, but a point about desires. Two desires made at different times are allowed to be contradictory, and we don't even need to bring up wireheading or fancy technology. This phenomenon occurs all the time. We call it regret or changing our mind.

So you have rebutted a common objection to the claim that someone does not want to wirehead. But it doesn't follow from that that your beliefs about your desires in general, or desires to wirehead in particular, are infallible. Given certain conceptions of what desire/preference means and certain assumptions about the transparency of mental content it might follow that you can't be wrong about desires (to wirehead and otherwise). But that hasn't been shown in the OP even though that seems to be the claim the title is making.