This one has 15/59 of the commentary messages.
So that means after you finish it, the achievement must be 15/59 (duh...).

Node 1/59 :



Just behind you as you start the game.

Node 2/59 :



Inside the small house.

Node 3/59 :

On the little crossroad, take the left path and you will find the 3rd message.




Node 4/59 :

This and the 5th one are very close and pretty much you can't miss them.



Node 5/59 :



Node 6/59 :

Follow the path behind the big rock near the shore and you'll find the 7th one :



Node 7/59 :

This is at the end of the path near the array of rocks near the tunnel. You can't enter the tunnel by the way, but you might find some books near there.



Node 8/59 :

Turn back, and right where you found the 4th and 5th commentary clouds, look on the mountain and follow that path. There you'll find Node #8.



Node 9/59 :

As you take a left turn on the hill to ascend you'll find one more node



Node 10/59 :

The next few can't be missed



Node 11/59 :



Node 12/59 :



Node 13/59 :

This one's pretty easy too. Just needed to say that there's no point in entering the cave. Just go to the left path to get #14.



Node 14/59 :



Node 15/59 :

At the Stonehenge-y place you'll find the last node of the first chapter :



Next 3 parts coming soon...

Here you can find 14 developer comments.
So after you finish this chapter, the achievement should be at 29/59.

The first one is right at the start.
Take it and you'll have 16/59 :




For 17/59, just take the left path after. Follow this path to the end and you'll also find 18/59 :







You can find 19/59, as you stroll in the middle of the shipwreck. Pretty unmissable.



For 20/59, just go to the right of the previous picture and you'll find it behind the empty container.



21/59:



As you go uphill, there's a little crossroad. Take the right path and right where the pit is you'll find the 21st node.

22/59:



Up the path for the bothy, you'll find some small sheep house. On the front you'll find this.

23/59:



As you reach the top of the hill, to the abandoned Shepherd's house, inside it you'll find the 23rd.

24/59:



Cross the door to the other side and on your right moving away from the bothy, you'll find commentary 24.

25/59:



As you go down, near the cliffside you'll find #25. Can't really miss that one.

26/59:



Some dozens steps away down that same path, you'll find #26.

27/59:



On the destroyed wooden ship you'll find the next one. In your path, can't miss it.

28/59:



Attention on this one cause if you focus on the cave where you have to enter, you might miss this one (i did on my first commentary hunt). So after #27 take a right turn and walk through the mountain.

29/59:



The last one can't be missed. Take it and prepare to enter Chapter 3.

The part with the caves has 14 more commentary spots.
This should get you at 43/59 once you're done with the chapter.

30/59:



Right at the start, you'll find the 30th node.

31/59:

When you reach the cave with the stalagmites you'll find #31.
No need to go inside that place, as you won't find anything



32/59:



Right at the 31st node, take a left turn (almost 180 degrees) and follow the upward path. Right before the fall to the pit you'll find Node 32.

33/59:



As you swim up the small lake, and enter the passage, you'll reach #33.

34/59:



Go round that curved path on your left (don't fall down to that same lake again!) and there is the 34th Node.

35/59:



After #34, enter the passage and you'll eventually find #35.

36/59:



Entering the next sector, you'll find #36 on a stony bridge with a river under it.

37/59:



Cross the bridge to the end and you'll find an upward path on your left that leads to Commentary Node #37.

38/59:



When you reach the star-like wall you'll take the next one.

39/59:



Right before the path with the luminous messages on the walls is Node #39.

40/59:



You'll find a small pond and as you enter it on your left below it's surface is the 40th cloud.

41/59 and 42/59:





Be careful as the next two are in a different part and if you wander off and explore the highway, there's a chance you might miss one or both of the nodes.
I know i did the first time i entered the Highway.

It really seems to be based on luck (if this map is timed or not).

43/59:



After the highway, you'll find the last node of Chapter 3.

The last part of the game has 16 more commentary nodes.
Watch out, as there's one that you can't find that easily.

44/59:



Right where you start. Can't miss it.

45/59:



Take the left path and you'll find this one. You can't go any further on the left, so take the right path after this.

46/59:



On a small wooden pier, you can find the 3rd node of the chapter.

47/59:

Now go back to the start of this chapter where you found Node #44. Take the right path this time and after much walking ...



...you'll come across #47. By the way, what is that?




48/59:

Follow this path to the end and you'll find #48.



49/59:



Go on the path along the mountain and you'll find #49.

50/59:



On the end of that path as you see the small port with the wooden boat and the origamis, there's Node #50.

51/59:



Up those stairs, and as you walk up that mountainside, you'll get #51. Can't miss it.

52/59:



A few metres after #51, turn 180 degrees left and take the path with the rail tracks. At the end of the path you'll find #52.

53/59:



Go back to your "normal route" (that's up the mountainside, heading for the beacon) and you'll come across node #53.

54/59:



A few dozen metres the last one you'll find #54. Watch on your right as you can slightly see the next one.

55/59:

Here's a better view of #55 with some weird entity near it :



And here's #55 up close :



56/59:



After you took your time and enjoyed the view from that peak, go back to the mountainside and after a while as the path narrows and the color pallette changes slightly, you'll find the 56th node.

57/59:



This one is just before you reach the last house.

58/59:



As the fenced stairs start you'll see Node #58. Can't miss it.

59/59:



Walk a few steps more and you'll find the last one.

Once you get #59 you should get the achievement.
Note that there's also one more commentary node, just before the end, but it does NOT count toward the achievement. Therefore it doesn't have a yellow cloud. It's just the devs thanking you for taking the time to buy and play the game.

I wanna thank the following people for this guide :

Yiab,
Zowieanna Zanthia,
THE TENTH,
[x] Zmey,
Annexed, <----- He has a nice trick to track down the progress of the achievement. Check his comment out.
Storm_at_Sea,
Enrique (old harry),
proudlarry