Note that the parent comment isn’t saying it couldn’t be a real phenomenon, just that you need proper studies to distinguish it from people’s general tendency to wrongly attribute causation. Assuming there exists a group of post-covid patients who have prolonged symptoms, it’s in their best interests that there be a proper study, with a robust case definition. Otherwise, we’re unlikely to find any therapeutic interventions that will help these people, because any actual therapeutic benefit may be drowned out by potentially large numbers of other people who have similar symptoms but not the same etiology.

FWIW, I’m an ER doc and see lot’s of covid and post-covid patients, as well as working with lots of staff who have had it - for most people, the after-effects last longer than a bad flu, but not as long as, say, after getting a bacterial pneumonia. But it’s certainly plausible that covid could cause prolonged symptoms (3-6 months) in some patients.

So the way to “take these patients seriously” is not to assume their prolonged symptoms must be due to covid, but to consider that they might be due to covid...and then use that to motivate a study that actually investigates the phenomenon.