I read somewhere (and have since lost the link), that concentration practice expands the sense of self to include 'other', whereas insight practice is about dissolution of self.

Is this a reasonable definition?

Is it possible that the author was speaking specifically about Metta practice or the Brahma Viharas? Those practices are usually done as concentration practice and can definitely expand the sense of self to include other, others, the world, etc.

Those two weren't mentioned, but thanks, those are two things I haven't given any attention as yet.