I use the below SWQL query to return all muted nodes in the environment. Includes the username of the person that muted the node.
SELECT n.Caption AS [Node] ,n.DetailsURL AS [_LinkFor_Node] ,'/Orion/images/StatusIcons/Small-' + n.StatusLED AS [_IconFor_Node] ,tostring(tolocal(SuppressFrom)) as [From] ,case when SuppressUntil is null or SuppressUntil = '9999-01-01 00:00:00' then 'Not set' else tostring(tolocal(SuppressUntil )) end AS [Until] ,case when SuppressUntil is null or SuppressUntil = '9999-01-01 00:00:00' then '-' else tostring(daydiff(getutcdate(), asup.SuppressUntil)) end as [Days Left] , ae.AccountID AS [Muted By] FROM Orion.AlertSuppression asup join orion.nodes n on asup.entityuri=n.uri join ( SELECT ae.NetObjectID, max(ae.timeloggedutc) as recent FROM Orion.AuditingEvents ae WHERE ae.auditingactiontype.actiontype in ('Orion.AlertSuppressionChanged','Orion.AlertSuppressionAdded') group BY ae.netobjectid) mostrecent ON mostrecent.NetObjectID = n.NodeID join ( SELECT ae.NetObjectID, ae.AccountID, ae.timeloggedutc FROM Orion.AuditingEvents ae WHERE ae.auditingactiontype.actiontype in ('Orion.AlertSuppressionChanged','Orion.AlertSuppressionAdded') Order BY ae.TimeLoggedUtc desc) ae ON ae.NetObjectID = n.NodeID and ae.timeloggedutc=mostrecent.recent order by n.caption