Chaplin
Better off silent
Sayid is really hard to figure it could have been that after plunging the knife into MIB and seeing nothing happened, and then not being killed, he simply did the math and said I need to be on this guys good side?
Dogen had already tried to kill him and I agree he sent Sayid to kill MIB fully aware it probably wouldn't work, he just expected if it didn't, Sayid would be killed. I guess we're supposed to wonder if Sayid had stabbed him BEFORE MIB said "hello Sayid" he would have died? Dogen immediately said to Sayid you let him talk, and Sayid said only after I stabbed him, but that wasn't true he said hello Sayid first.
I'm still on the fence it's not clear that it's really black and white good vs evil I'm thinking along the lines Gad mentioned there's no clear good or evil both guys are shades of both. I think some of the characters like Kate are still not sure where they stand because they don't know who to believe either.
For Kate, it's all about Claire. My guess, and it's just a guess, is that Kate's mission now will be to make Claire sane again. She did tell Claire she was there to get her so she and Aaron could be together again, but it was obvious Claire didn't believe her or didn't care (which makes no sense).