Delete comment - actually delete it, or create `deleted` column and update it?
I'd say this depends on the set requirements - many projects demand that the database never forgets "things" - to be able to generate reports and so on. In these cases you usually have this deleted column already. On delete you update said column - and for the report-functions you have an additional table that keeps record of who "ordered the delete" (just in case "he" deleted something that wasn't meant to be forgotten).