Keep some context displayed on collapsed comments for reference (in full-collapse mode)

[elishamint]

Description v. 0.0.33 Collapsed comments, in full-collapse mode, currently show only user name and number of comments in the collapsed sub-tree. It would help navigation a lot if we would have at least some (truncated) text from the collapsed comment shown, possibly 1-2 lines in small font. It should not take up much more display space than it currently does