Stative, locative etc etc

The two measly word sets that are used as evidence that pre-pre-PIE
was stative and therefore for a thing had separate lexical entries
for it qua active agent and qua passive object are agni-/fire and
aqua-/water. For some odd reason both "passive entries" are -r/-n
heteroclitic stems. Now what's that about? Why would "fire"
and "water" need a nominative (once ergative?) if they already had an
agent? Something fishy is going on.

It occurred to me that all the -r/-n stems I know refer to
uncountable stuff, masses. Such that an interpretation of *-r as
originally not an ergative or nominative marker, but a locative
marker, makes sense.

Thus not

"the water rushes" but
"in-the-water there-is-rushing"

which fits nicely with an interpretation of 3rd sg *-ti as a
participal suffix

"in-the-water (there-is-)rushing"

(or "in-the-blood", "in-the-liver", "in-the-thigh", "on-the-road")

Besides:
Germanic here, there, where. All with a locative r-suffix. And they
can be (pseudo-)subjects to boot: here is ..., there is ..., where
is ..., Danish even with arbitrary verbs: her optræder <noun> "here
performs <noun>" etc. And they occur as place-holders in preposition-
neuter pronoun phrases: thereof, hereafter, wherewith. Dutch shows
the loosest association between "locativic pronoun" and pre-(and in
this case post-)position/preverb, so that the latter is almost back
in its original function as adverb:

"Waar praat je over?" >
*"What talk you about?" ie "What are you talking about"

Torsten