There are really too many digressions to mention. If you need to look at certain sections, think of anything beyond the few days he's describing between Pencey and his eventual stay in the hospital. Anything about Jane or Allie or James Castle or anything else like that.
It can be argued that Holden is not a bad communicator. In fact, he is telling the entire story of the past few days to a doctor at a "rest home" in California. You can see that in the framing device of the novel.
However, Holden tells the story with many digressions. He is known for that. When he was giving speeches in one of his prep school classes, the teacher used to yell "digression" at him. However, as readers, we are thankful for the digressions. These tangents to the story enrich our understanding of Holden and his struggles from the time that he is asked to leave Pencey until he allows Phoebe to fend for herself on the Central Park carousel, a metaphor that shows he has given up on his fantasy of protecting childhood innocence and being a "catcher in the rye."
Another thing that complicates Holden's communication is this desire to protect childhood and his refusal to grow up. This is why he sees all adults as phonies. He sees everyone other than a few characters (Jane, Allie, Phoebe, etc.) as pure. Anyone who is a little older and has learned to "play the game" that we all do to get by under the expectations of society is a phony to Holden. There is some irony here, of course, because we see Holden's phoniness at different points in the novel.
Can you tell me, where on wich site and aon wich chapter on we see his bad communication??