Status: IN
Social graph symmetry is the enabling constraint for lightweight write-time routing: because relationships are always bidirectional, write-time routing decisions (who receives fan-out, who sees nearby friends) are fully determined by a single graph traversal — the combination of symmetric relationships with irrevocable reference-based fan-out eliminates the need for read-time routing correction that asymmetric follow graphs would require.
Social symmetry (d2) guarantees routing completeness; lightweight-but-binding writes (d2) guarantee routing finality — together they mean no read-time correction is needed
Depends on (SL): social-systems-combine-symmetric-graphs-and-lightweight-fanout, write-time-decisions-are-lightweight-but-binding