Level of detail when reviewing a PhD thesis - very picky (draft) reviewer I am currently finalizing my written PhD thesis. I think in practice it is often the case, that a PhD student has a formal advisor (often head of the lab, very busy) and then an actual advisor who is much more familiar with the PhD's work and progress. Often this actual advisor is a PostDoc and the student has regular meetings with him. This is also the case for me. With the PostDoc I have weekly meetings. I meet my formal advisor unregularly/randomly, about once a month.

So, I finished a first complete draft of my thesis and handed it in to my formal advisor, because he is my official advisor. As expected my formal advisor sent the draft to my actual advisor. My formal advisor is often traveling and very very busy. So I did never expect him to read the full thesis, let alone providing detailed review of my work.

The thing is, that I know that my actual advisor can be very picky about language stuff and how scientific texts are written. I know this from writing papers together with him which was always somewhat cumbersome due to his over-detailed reviews. His reviews were always very thorough causing some headache and also sometimes a shaking head on my side.

So today I received a first review from him just for the introduction chapter which is about 15% of my thesis. His review is extremely detailed, he picks on each sentence, and often even words. He critisizes the word order of my sentences and questions every argument I make. He tries to be perfectionist. The result is for me, that I feel really bad when discussing the review with him. It is frustrating to get corrected that thoroughly and it makes me think, that I am too dumb for this. Moreover, I am sure that my quality of writing and lines of argumentation have a decent level of quality and I think he is over-interpreting most things. Of course, I try to not take the feedback personally, and see it as an opportunity to improve my work. However, I think his level of detail is a bit too much. It also means a lot of work for me (to correct everything) and I think, it will take at least 2 more months to hand in a final version.

One example of his reviewing, which I know from a colleague of mine: My colleague needed to verbally express that two things are connected. The reviewer suggested to use the word link instead of connect. My colleague followed the advice and replaced all instances of connect with link. At the next reviewing iteration, the same reviewer suggested to replace all instances of link with connect again... So you know what I mean? It's just too much and he even seems to have different opinions when reading the same text a second time.

I also want to make clear, that I am very sure, that my formal professor does not doubt my academic qualities. For instance, he is aware that I received a Best Paper Award for one of my papers and we always have nice discussions about different research topics. Hence, I think he would not deem it necessary to have my thesis reviewed that thoroughly. I think, if I would confront my formal advisor with the review of my actual advisor, he would be stunned.

Finally, my question is: Is it normal that a thesis gets reviewed that thoroughly, even when the advisor knows me (and the quality of my work)? 

And more importantly: How should I proceed? 
I obviously want to get this done really quick. Of course, I know that reviews are essential to improve the quality of my thesis and I am willing to put in substantial amount of time. But I think it's too much, if I need to change (nearly) each sentence of what I have written...
Should I talk with my formal advisor about that? What should I let him know?
This type of question doesn't have a single correct answer, but many different approaches. To that extent, here's what I would do.

There's two ways to go here: the difficult one, where you try to fight back, and the easy one, where you just make the corrections. Given that (a) this is a thesis, not a publication, making it essentially a single-purpose document unlikely to be referenced again in the future, and (b) the completion of the thesis is entirely dependent on this picky advisor saying that it's complete, I would DEFINITELY recommend just making the corrections.

Stated differently: choosing to fight this will likely cause far more damage than choosing not to fight.

Only caveat to the above is to only let this happen once or maybe twice per section. I.e., if this goes on for two rounds—i.e., if you make all his changes, and then he gives you another redlined document, where he essentially edits most of his own edits—then you're in infinite editing purgatory, and you'll have to work with him to figure out how to break the cycle and agree it's just good enough.