This is Quirk's I presume. I would say that it is about discourse markers so...
The style disjunct is in the phrase: From my personal observation,
The statement is: he neglects his children.
Style: formal/informal etc
Form: grammatical forms such as modal, passive, perfective, negative, positive etc
The phrase "my personal observation" changes the "authoritative" sense of the statement. It is a personal observation, rather than say a widely recognised observation, so it is more subjective.
Student or Learner