The pasuk we quote in Kedusha from Yeshayahu 6:3 reads וְקָרָ֨א זֶ֤ה אֶל־זֶה֙ וְאָמַ֔ר קָד֧וֹשׁ ׀ קָד֛וֹשׁ קָד֖וֹשׁ יְהוָ֣ה צְבָא֑וֹת מְלֹ֥א כָל־הָאָ֖רֶץ כְּבוֹדֽוֹ׃
In this pasuk, the image I understand is the Seraphim singing the praises of Hashem. They turn to each other and say "Holy."
The trope seems to connect the first 2 iterations of "kadosh" which would make sense if we imagine the Seraphim speaking one to the other and then the other to the first. The third "kadosh" would be a statement said in unison introducing the final concept. The darga-tvir combination seems distinct from the tipcha-munach-etnachta. The meaning would then be (as Chabad's translation has it) ""Holy, holy, holy is the Lord of Hosts;"
When it is read, then, there should be a slight pause between the second and third statements, but I often hear people singing and reciting the three "Kadosh" statements together and then starting "hashem tzeva-ot" as a new phrase.
The Koren siddur, in the bracha of Yotzer Ohr for weekdays has a comma after the first 2 "Kadosh" statements and then none after the third, allowing it to run into the "hashem..." statement. In Kedusha for shacharit, though, there is a comma after each of the three and this is also the case in the Kedusha Desidra. My Siddur Tefillah Hashalem has 3 commas in Kedushat Yotzer and 1 comma in the shmoneh esrei -- after the third Kadosh. The first Artscroll I found (and I don't know if there is consistency across Artscroll texts) was the Machzor for Sukkot and it has no commas.
Is there a difference in meaning intended by different ways of splitting up the three words?