You can link to a topic with just the number: /topic/1. Everything after that is fine. If your browser copy pastes urls like that there isn't much else that can be done.
Is there any way to see how many posts were added in a specific date range?
We only show last day,week, month on the dashboard. I think we should allow a bit more flexibility to see any date range.
In the meantime this will give you the number of posts created between
db.sortedSetCount('posts:pid', min, max, callback);
maxwith a unix timestamp in milliseconds.
I mention that here, too: https://community.nodebb.org/topic/13972/