Mixed use of titles in dissertation acknowledgment I would of course use Prof. and Dr. in front of the names of committee members and other professors who I call by Prof. and Dr. in real life. But what about your “peers” who have doctorates?
For example, in the first paragraph I thank my advisor,  Prof. John Smith.... then in the next paragraph I mention specific people who helped me including Dr. Wang (a mentor at a different school) and Johny McLovin (who now has a PhD but worked with me as a grad student in the same lab). Then in the next paragraph I thank my friends and most of them have doctorates also but I’d just put their first names only. It kind of makes sense to me but the inconsistency bothers me. Most importantly, would it be rude to do this? Because in the same sentence I am referring to someone as a doctor and the other as not when both have doctorates purely based on my personal relationship.
On the other hand, I have read an acknowledgment that included titles in front of every single name (including Mr. and Ms.) and it bothered me a lot.
And no, I cannot just leave out the titles altogether because it’s something not culturally acceptable at my institution.
I have seen similar questions here before but none of them were directly applicable to my situation.
I'd suggest that if a person has a doctorate that you should give the title, even if they are your friends. It honors their achievement.
Your dissertation will be read by others, possibly many others if it is published.