What plot points were just casually ignored by the LOST writers due to how nonsensical they were?

In Stargate, first instance, they introduced a lot of things and backtracked on them solely because they simply didn't work.

The two women from the Others (Mrs Clu/Klough/whatever, and the older leader lady) who were introduced then dropped just as fast and Jack's tattoo are infamous ones.

I feel like Room 23 served zero purpose at all and it appears the writers thought the same as it never became anything bigger