Right now the only way to get this is to follow the link to the post that was merited and do additional scraping, but it just creates unnecessary load and is messy to implement.
What's really going to get you, is if the Merited post was made on a hidden board (most likely the VIP or Staff board). It'll look like the post was deleted, and you'll have to correct it after
theymos' weekly Merit data dump.
Did theymos ever said anything about scraping in general - what's his stance on it?
I haven't read anything about it, but if you go faster than 1 request per second, you'll hit a timeout.