I don't know. Talk to somebody and exit the conversation, trade for a couple minutes, talk again and check the conversation log. If there is a 30 second, or so, difference between conversations, then trading doesn't count.
I believe the time you're in the "trade mode" with a NPC doesn't count for the total time of all your conversations ... but even
without this "shopping time of my Priestly-big-pleasure Trading Tour of Ronja" ... now at level 32 I've a total time on Conversations around (above) 70 hours !!
that very impressive !
But to say this:
I don't SKIP dialogs, except with my runners sometimes I do .
Love to hear what NPC's say and how they speak

Most are o so funny, especially Zixzax, Timpuk, Charlie (on his island), Hermit, the Illusionist's and many more !!