In the end, whatever we think we think, we all end up with an interpretation of events, especially fictional events. At this point, I can think whatever I like about Lost that doesn't contradict what was shown. E.g. I can think that the black smoke is not smoke, but merely looks like it, but I cannot think it was Jacob in John Locke's visage.
So for example I do not believe the black smoke was smoke. It may look a bit like smoke, but smoke does not look like that. To me, it looks like charged particles moving on magnetic field lines. If MiB is made of energy, and can therefore control himself as a cloud of energy, then the smoke is really black magnetic crushed volcanic rock and ash. The magnetism is so powerful there is sound from the internal collisions, mixed with constant static discharge. And he accidentally picked up a chain in there. Oops.
See, the facts of the show support that theory and I prefer it to "answers are bad, don't find one". Unlike reality, to which we can return and find further information, you cannot do that with a work of fiction. It can be rewritten, but that's another show. A sequel can be made, but perhaps by different people, causing a fork in canon (i.e. the same with official but separate fictional spaces, like Star Wars Novels). So you have the facts as they are... and like reality you can form a number of theories to fit them. In reality you check back to see which theory fits NEW data, but lacking new data you can simply choose one. I personally choose ones that rely on the fewest principles, and ideally bring in nothing that doesn't have some analog, at least, in the work of fiction being considered.