Adding a ?a=1 to get around HN's dupe detector is unwise.
EDIT: Per dang's response below, this is OK since there has not been significant discussion on it previously.
EDIT: Per dang's response below, this is OK since there has not been significant discussion on it previously.
A small number of reposts is ok if a story hasn't had significant attention within the last year or so. Otherwise, what reaches the front page is too affected by randomness and churn. We want the best stories on the front page, not just the luckiest ones. So good stories need multiple cracks at the bat. Especially the Show HNs—a new feature for which is coming soon, by the way.
When we release the Show HN feature (soon!) it will come with some guidelines about what is and isn't a Show HN.