_normalize_reddit, _normalize_hackernews, and _normalize_github inlined
the same 5-line comprehension to stringify and space-join the first 3
top_comments' excerpt field. Extract one helper, call it from all three.
The comment field name varies per source (Reddit/GitHub use 'excerpt',
HN uses 'text'), so it's passed as a parameter. Behavior unchanged.
Ilia Alshanetsky
2c2755b49c