Doubling pawns can cramp a pawn chains ability to flex or go forward. It can create targets. It can close sections of the board so pieces cannot switch through that area. On the other hand, it can open files for rooks. It can be beneficial as long as the capture is towards the centre, for example certain positions with pawns on e5 and e6 can be very hard to break down, or ones with the h pawn capturing on the g file. Pros and cons, like so much in this lovely game of ours, depending on the exact position and pieces involved that can exploit the weaknesses.
Having said that, true glory is in the tripled pawn. I rejoice when I can triple someones pawns but I am truly elated in those rare games where I accept tripled pawns myself and go on to win.
Doubled pawns can also eventual undouble.
I don't get why the knight has to be placed on d5 to begin with. I would have gone with parking the rook on d5 and tried to double up on that file. This seems much more sensible to me. At the very least, there's no hurry for white to place the knight on the d5 outpost immediately like what's shown in the diagrams since that removes the defense of the c4 pawn.
It's chess tactics 101.
Nd5 is a good place for the knight.
I don't get it. Please elaborate.
I am well aware that knights belong on good outposts, and d5 happens to be an excellent one. I just believe that the rook can make better use of it, and the knight is doing a fine job staying right where it is. Especially because the isolated doubled pawns can become easy targets for the opposing knight, keeping the white knight on e3 for the time being seems very sensible. It seems like you're not taking everything into account and making decisions simply by principles alone.
Well, it has to do with the fact that black is to move, not white.