I have the following table structure:

So each forum post has a parent,
WITH RecursiveCte AS
(
SELECT 1 AS LEVEL,
H1.intUserId,
H1.intReportsTo,
H1.strUserName
FROM mstUsers H1
WHERE id = @intUserId
UNION ALL
SELECT RCTE.level + 1 AS LEVEL,
H2.intUserId,
H2.intReportsTo,
H2.strUserName
FROM mstUsers H2
INNER JOIN RecursiveCte RCTE
ON H2.intReportsTo = RCTE.
)
SELECT intUserId,strUserName,LEVEL FROM RecursiveCte