Whether the person in the article practised incorrectly or not is not really the issue. The narrative on and praise for mindfulness in recent years has not included any warnings that there may be dangers. Quite the opposite, it is usually posited as an unambiguous positive.
Your idea that this person was 'doing it wrong' is quite a hand-wavy posture to start with, especially as the author finds that such problems have been described by experienced practitioners.
> Lauded by whom?
The article mentions whom - the various interested parties in mindfulness, the great and the good that attend and throw conferences, those that throw workshops and run retreats. To some extent mainstream journalism and society at large, and even hacker news - mindfulness has been favourably covered here and in a variety of other places over the last several years, never have I seen a warning that you may experience mental health problems if you do it badly, or too much, or whatever.
> Those are very different and learning from an experienced practitioner is important.
Oh I'm sure they are, and I'm sure it is. Do you have evidence that the author was not learning from experienced practitioners? Or are you merely knee-jerking to the defence of something you personally like?