i see people do it all the time and it seems like it could make it dull quicker
is it bad for knife to push food around with it?
It's not on the officially approved activity list, but it's not particularly harmful compared to a lot of the stuff people get up to with their knifes, and everyone does it.
Chef Ross is right that it can make your knife dull over time. The way to deal with that though is not to run for a board scraper everytime you dice a spud, but to sharpen your knife before it gets dull.
Hope this helps,