大般涅槃經義記 3.262

3.262

In the first clause, 'taking non-suffering as suffering is called inversion' generally designates it; below, it explains its characteristics. 'Non-suffering' is the Tathāgata, explaining what they are deluded about. 'Those who generate inverted notions' refers to [taking] the Buddha as impermanent, revealing what they assert: impermanent, therefore suffering.