Truncated notes in Contacts
Notes in Contacts get truncated after about five lines. This has been reported before for High Sierra, but the solution seems to have been merely to terminate the discussion.
Because of my extreme self-discipline and restraint, I withhold any further discussion of this fault in the program, except to note that this case goes into my file on how truly stupid computer programmers can be in practical matters.
iMac, OS X Yosemite (10.10.4)