From what I've read from other posters, it seems to be hit or miss. Notes are sometimes not entered at all and if they are they may not be clear to the next rep.
From my own experience, notes from my interactions with CS are there. But I've never had any major issues or support sagas.
There may be a consistent policy. Who knows? Even if there is sometimes it's tough to get everyone to follow it.
Sorry you're having issues. I hope everything works out for you!