Here is Bhikkhu Bodhi's comments from the MN 18 translation:
“Bhikkhu, as to the source through which perceptions and notions [born of] mental proliferation beset a man: if nothing is found there to delight in, welcome and hold to, this is the end of the underlying tendency to lust, of the underlying tendency to aversion, of the underlying tendency to views, of the underlying tendency to doubt, of the underlying tendency to conceit, of the underlying tendency to desire for being, of the underlying tendency to ignorance; this is the end of resorting to rods and weapons, of quarrels, brawls, disputes, recrimination, malicious words, and false speech; here these evil unwholesome states cease without remainder.”
- BB: The interpretation of this cryptic passage hinges on the word papañca and the compound papañca-saññā-sankhā. Ñm had translated the former as “diversification” and the latter as “calculations about perceptions of diversification.” It seems, however, that the primary problem to which the term papañca points is not “diversification,” which may be quite in place when the sensory field itself displays diversity, but the propensity of the worldling’s imagination to erupt in an effusion of mental commentary that obscures the bare data of cognition. In a penetrative study, Concept and Reality in Early Buddhism, Bhikkhu Ñā˚ananda explains papañca as “conceptual proliferation,” and I follow him in substituting “proliferation” for Ñm’s “diversification.” The commentaries identify the springs of this proliferation as the three factors—craving, conceit, and views—on account of which the mind “embellishes” experience by interpreting it in terms of “mine,” “I” and “my self.” Papañca is thus closely akin to maññanā, “conceiving,” in MN 1—see n.6:
The compound papañca-saññā-sankhā is more problematic. Ven. Ñā˚ananda interprets it to mean “concepts characterised by the mind’s prolific tendency,” but this explanation still leaves the word saññā out of account. MA glosses sankhā by koṭṭhāsa, “portion,” and says that saññā is either perception associated with papañca or papañca itself. I go along with Ñā˚ananda in taking sankhā to mean concept or notion (Ñm’s “calculation” is too literal) rather than portion. My decision to treat saññā-sankhā as a dvanda compound, “perceptions and notions ,” may be questioned, but as the expression papañca-saññā-sankhā occurs but rarely in the Canon and is never verbally analysed, no rendering is utterly beyond doubt. On alternative interpretations of its components, the expression might have been rendered “notions [arisen from] the proliferation of perceptions” or “perceptual notions [arisen from] proliferation.”
- The Pali verb “conceives” (maññati), from the root man, “to think,” is often used in the Pali suttas to mean distortional thinking—thought that ascribes to its object characteristics and a significance derived not from the object itself, but from one’s own subjective imaginings. The cognitive distortion introduced by conceiving consists, in brief, in the intrusion of the egocentric perspective into the experience already slightly distorted by spontaneous perception. ...
The sequel will make it clear that the process of cognition is itself “the source through which perceptions and notions [born of] mental proliferation beset a man.” If nothing in the process of cognition is found to delight in, to welcome, or to hold to, the underlying tendencies of the defilements will come to an end.
“Dependent on the eye and forms, eye-consciousness arises. The meeting of the three is contact. With contact as condition there is feeling. What one feels, that one perceives.  What one perceives, that one thinks about. What one thinks about, that one mentally proliferates. With what one has mentally proliferated as the source, perceptions and notions [born of] mental proliferation beset a man with respect to past, future, and present forms cognizable through the eye.
- BB: This passage shows how papañca, emerging from the process of cognition, gives rise to perceptions and notions that overwhelm and victimise their hapless creator. Ms contains a note by Ñm: “The meeting of eye, form, and eye-consciousness is called contact. Contact, according to dependent origination, is the principal condition of feeling. Feeling and perception are inseparable:
MN 43.9 http://www.accesstoinsight.org/tipitaka ... .than.html
- "Feeling, perception, & consciousness are conjoined, friend, not disjoined....
What is perceived as ‘this’ is thought about in its differences and is thus diversified from ‘that’ and from ‘me.’ This diversification—involving craving for form, wrong view about permanence of form, etc., and the conceit ‘I am’—leads to preoccupation with calculating the desirability of past and present forms with a view to obtaining desirable forms in the future. ” Perhaps the key to the interpretation of this passage is Ven. Mahā Kaccāna’s explanation of the Bhaddekaratta verses in MN 133. [http://www.metta.lk/tipitaka/2Sutta-Pit ... tta-e.html] There too delight in the elements of cognition plays a prominent role in causing bondage, and the elaboration of the verses in terms of the three periods of time links up with the reference to the three times in this sutta.