In Rev 25, the following Sections are numbered 0.
12.2.0 Semantics (in 12.2 Primary Expression)
13.0 Statement Semantics
13.6.0 Semantics (in: 13.6 Iteration Statements)
15.2.0 Module Static Semantics
This is a duplicate of Bug 2138, which is marked as Invalid. Still, it is odd, and one could simply start regularly at 1.
I no, and I still don't intend to change it.
I use that convention when initial subsection relates to the enclosing section in a manner that is different from the other subsections that immediately follow.
For example, 12.2.0 are semantics that relate to all of the rules in the 12.2 grammar productions while the rest of the 12.2.x subsections each group semantics that apply to one of the productions of that grammar.
The most conventional thing would be to promote 12.2.0.1-12.2.0.4 a level, but that would but individual semantic rules at the same level as the rule groupings that follow.
It's not something that I intend to further tweak for this edition.