If I understand you, you want members to see *ALL* their own postings but only "active" postings from other members, right?
It's still trivial.
memberid = $currentMemberId
OR updated > DATE_SUB( CURDATE(), INTERVAL 5 DAY )
is all that is needed.
Note how I enclosed the OR
ed conditions in parentheses. If there are any other conditions in the WHERE you *need* those parentheses. They can only be omitted if there are no other WHERE conditions. I recommend always including them.