Generally people on Less Wrong use "belief" to refer to objective beliefs rather than opinions, as it seems to be a better way to carve reality reality along its joints. There's no reason to assume that other people will adhere to this convention though.

So for a particular statement X, a rationalist will put it into one of two categories:

• A mixture of 1 and 3 for different people: some people expressing belief in X have a low confidence, others believe they believe X
• 2: people expressing belief in X are expressing an opinion

The first is for facty statements, the second for subjective ones.