incorporate clarification on secret rooms
@@ -147,7 +147,9 @@ relationship can be expressed in one of two ways:
To avoid abuse where a room admin falsely claims that a room is part of a
space that it should not be, clients could ignore such `m.space.parent`
events unless their sender has a sufficient power-level to send an
- `m.space.child` event in the parent.
+ `m.space.child` event in the parent. The rationale for checking the power
+ level, rather than the *actual* presence of an `m.space.child` event in the
+ parent, is to accommodate "secret" rooms (see below).
Where the parent space also claims a parent, clients can recursively peek
into the grandparent space, and so on.
