I can't comment on what's been said over at DO. I think their re-interpretation of Mahasi Sayadaw's works are curious - to put it euphemistically.
It is true that both samatha and vipassana meditation can become unpleasant as we become increasingly more aware of deeper and more subtle aspects of our mental and physical matrix. I sometimes refer to going off on retreat to my non-Buddhist friends as 'going away to commune with my demons'. So, yes, samatha and vipassana can cause difficulties such as hindrances to manifest, physical pain, intense physical and mental pleasure as well as extremely intense emotional states to manifest.
It is also a prescient reminder that meditation isn't about taking time out to experience bliss, perhaps like in some other traditions, but is about developing wholesome mental culture.
So, I think its important to try and balance aspects of our practice. Not only sila, samadhi and panna, but also ensuring that we balance the faculties (indriya): saddha (faith/confidence), panna (insight/wisdom), energy (viriya) and concentration (samadhi), and mindfulness (sati).
“No lists of things to be done. The day providential to itself. The hour. There is no later. This is later. All things of grace and beauty such that one holds them to one's heart have a common provenance in pain. Their birth in grief and ashes.”
- Cormac McCarthy, The Road
Learn this from the waters:
in mountain clefts and chasms,
loud gush the streamlets,
but great rivers flow silently.
- Sutta Nipata 3.725Compassionate Hands Foundation
(Buddhist aid in Myanmar) • Buddhist Global Relief