I have seen:

      Oran, ki sen bugün gördün, benim en iyi arkadaşım.

Since Turkish uses adjective constructions, it seems that the preferred structure would be:

      Bugün gördiğin Oran en iyi arkadaşım.

I thought that ki was to be used with caution and reserved for statements like:

      Ne yazık ki gelmedin.

Although perhaps the better form here would also be:

      Gelmediğin ne yazık.

Are these sentences acceptable because the clauses are parenthetical?

I took the turkish explanation from the site below.

http://www.ihvanforum.org/showthread.php?t=77688&page=1

I am not very well at English but I think the sample can be understandable.

I hope it helps.

Kİ BAĞLACI
Kİ CONJUCNTION

(there seem 3 types of using)

*Özneyi pekiştirir.

*It reinforces the subject.

---Ben ki yedi iklimin padişahıyım. 

---Me, who is the emperor of the 7 seasons. / I, the emperor of the seven season

---Sen ki Fransa eyaletinin valisisin. You, the governer of the state france

*Neden-sonuç vardır. There is cause - result

---Günü kötü geçmiş ki çok kızgın görünüyor.He looks very angry because he had a bad day.

---Sana değer veriyorum ki seninle konuşuyorum.

---I am talking to you because I value of you

*Kuşku,yakınma,şaşma,amaç-sonuç, tahmin

*Doubt, gripe, suprizing, purpose-result, guess.

---Beni tanımıyorsun ki…(Yakınma)

---But, you don´t know me (gripe)

---Kafamı bir kaldırdım ki onu karşımda gördüm.(Şaşma,)

--- As soon as I looked up, I saw him/her (suprising)

---Arabayı o çizmiş olabilir mi ki?(Kuşku)

---I wonder if he scratched the car?

---Sana iş buldum ki kimseye muhtaç olmayasın.(A-S)

--- I have found you a job, so you won´t be in a bind for none. (Purpose-result)

---Geç saatlere kadar çalışmış olmalı ki sabah uyanamamış. (tahmin)

---He/she coudn´t wake up this morning, he/she might work late (last night). (Guess)

Hallederiz,

    It is apparent that ki serves many idiomatic purposes. Thank you for the additional examples of its use.

si++,

   The first example follows what I have understood to be good Turkish. The second also seems better with gelmemen instead of gelmediğin, but to me, this is much more subtle.

Thank you both for the rapid reply.

Hallederiz,

    It is apparent that ki serves many idiomatic purposes. Thank you for the additional examples of its use.

si++,

   The first example follows what I have understood to be good Turkish. The second also seems better with gelmemen instead of gelmediğin, but to me, this is much more subtle.

Thank you both for the rapid reply.