While we're talking less(1) features, one I stumbled across a few years ago when wishing really hard that less supported an interactive regex line filter, was its interactive regex line filter:
&pattern
Which will: Display only lines which match the pattern; lines which do not match the pattern are not displayed. If pattern is empty (if you type & immediately followed by ENTER), any filtering is turned off, and all lines are displayed.
I'd prefer this followed a syntax closer to mutt's filters, and that the patterns were editable (e.g., typing '&' during a filter would show the currently extant filter for modification), but it's handy.
I'd prefer this followed a syntax closer to mutt's filters, and that the patterns were editable (e.g., typing '&' during a filter would show the currently extant filter for modification), but it's handy.