> The second construction, however, is more interesting. It's more common in
> speech than the other type, it's used specifically for statements of
> evidential value, and it's a few steps further forward on the way to
> becoming grammaticalized. It employs a special kind of complement clause,
> which is subordinated to the impersonal verb *trà* ‘exist’ and introduced
> by one of several specialized complementizers that indicate different
> levels of evidentiality. (These are diachronically derived from former
> possessed nouns, along the lines of "there is [the information source
> of]..."):
​I actually like the idea of using special complementizers a lot. It never
occurred to me before. I think it would be useful in a conlang like Ronc
Tyu in which evidentiality is optionally marked.

> Hope this is of interest to some of you. How do your conlangs form
> evidential statements? How many and which levels of evidentiality do they
> have? Are they expressed morphologically or periphrastically?

Evidentiality is something that is infinitely fascinating to me for no
particular reason. ​łaá siri marks information source obligatorily on all
main verbs of a clause morphologically. It distinguishes:

Direct (DIR): for general gnomic or accepted facts. Also used after the
information source (hearsay, etc.) of a statement has been introduced
earlier and is now understood, kind of like an "evidential anaphor."
​‘arusasaá łaa’-ła r-u-r-la’ú.
SENT\mother animal-ANIM  ABS-IMM-INVS-DIR\see
'Some animal has seen (my) mother (this is a fact which has been

Auditory/Reportative (RPRT): to express knowledge attained through hearsay
or hearing (like if you were to hear a noise).
‘arusasaá łaa’-ła r-u-r-raa’-la’u.
SENT\mother animal-ANIM ABS-IMM-INVS-RPRT-see
'I heard that some animal has seen (my) mother.'

Visual (VIS): to express knowledge attained by the speaker's sight.
‘arusasaá łaa’-ła l-u-r-’aa’-la’u.
SENT\mother animal-ANIM  NEAR-IMM-INVS-VIS-see
'I see that animal looking at (my) mother.'

Inferential/Speculative (INFR): this is a conflation of epistemic modality
with evidentiality, and it expresses uncertainty of an event's occurrence
or inference about an event's occurrence. There are two inferential
evidentials which differ only in the epistemic content, one being _raa-_
(certainty) and one being _łaa-_ (doubt).

‘arusasaá łaa’-ła r-u-r-raa-la’u.
SENT\mother  animal-ANIM  ABS-IMM-INVS-INFR-see
'I think some animal probably saw (my) mother.'

‘arusasaá łaa’-ła r-u-r-łaa-la’u.
SENT\mother animal-ANIM  ABS-IMM-INVS-INFR-see
'I doubt that some animal saw (my) mother.'

​There are also some different ways of asking yes/no questions with the
evidentials. And a verb unmarked for evidentiality is interpreted as