Problem is that filtering is complicated.
Example:
USER 1 - VALUE 1 - LOL
USER 1 - VALUE 1 - LOL
USER 1 - VALUE 1 - NOTLOL
USER 1 - VALUE 3 - LOL
USER 1 - VALUE 3 - LOL
USER 1 - VALUE 3 - NOTLOL
So for every VALUE, if NOTLOL appears, change all LOLs for this VALUE for this USER for NOTLOLs...