microblog module - problem with max characters
The title column of the {node} table is limited to 255 characters. Just because you change it in the UI doesn't mean that it can be saved like that in the database, unless you mess around with the database schema manually (and you should not do that).

I am not sure why that module is exposing itself as a node type, sounds rather strange to me. The only reason I can imagine is being able to rely on the node access system. But nodes are a rather heavy thing, there is a lot of overhead that seems unecessary to me for this use case.