Section 2.2 DITA markup is followed by a hanging paragraph.

That is if I say see Section 2.2 DITA markup, do I mean only the following two paragraphs or do I mean all of Section 2.2, including all of its subsections?

For clarity of reference 2.2 DITA markup should be followed by:

2.2.1 Introduction
(your current two paragraphs)
2.2.2 DITA topics
2.2.1.1 Introduction to DITA topics
2.2.1.2 The topic as the basic unit of information

Reasoning that if you accept the comment on consistent subsectioning and giving examples section headings, elimination of hanging paragraphs fits nicely with those tasks and makes the document more consistent in appearance. Not to mention easier to reference.