'sama' as pronoun

 'sama' is listed as both the reflexive and the reciprocal pronoun for toki pona, for "-self" and "each other".  That is, at some deeper level, the 'sama' as object arises from a more complex structure involving the subject as well.  The simplest cases are:

x li V e x  => x li V e sama

x li V e y, y li V e x => x en y li V e sama
(Some verbs are inherently reciprocal, e.g., 'wan', maybe 'unpa', so only one of the pair need be given.)

Similar rules will work for the case of prepositional objects, including the complements of prepositions as verbs and for modifiers.  But the details seem (to me, now) to get a bit messy, so I'll skip over them.

The case for modifiers and prepositions seems to be just what one expects, the same as above with "M (pi)x"  replacing "V e x" etc. through out, where M might be very complex, involving a verb, perhaps, and objects and other prepositions.  So the whole can be summed up as
x G x => x G sama
xG y, y G x => x en y G sama
There are surely some restrictions on these but just what are not yet clear.

Some complications can arise, ambiguities in fact.
given that is is (almost) always possible to drop the object of transitive verbs, with marginal loss of meaning,
x li V e y, y li V e x => x en y li V e sama => x en y li V

x li V e w => x li V  } => x en y li V [taso e sama ala]

y li V e z => y li V

 x li V e w, y li V e w => x en y li V e sama
(This is a more semantic or pragmatic rule, so probably has a lot of conditions on it.)