No I don't think here is any limit on users posts per day as far as I am concern I have submitted more than 350 posts one day and didn't have any limit problem... I am not confirm probably they have some limit on this forum only but there is not such limit in other e forums of this site
I suggest that you ask the admin or the moderator of this community. I believe after the Google Panda Issues, they've made some changes re: their regulations (not sure though) so as to prevent spammers bombarding this site with senseless stuff . As for me, I limit my posting from 5-10 per day to avoid being banned.
I don't think there is really a limit about how many posts that you can submit. As you know forum is a place people come to learn and to share what they've learned with others. If you are willing to be helpful in a forum and you are posting useful information and I don't really think that you can limit yourself as far as the amount of post you can submit is concerned. Even though Google has recently updated its algorithm that does not mean all your links are going to get indexed simultaneously.
Although you submit several posts every single day in a particular forum. Those links may take days to weeks before Google can find them and index them. If I were you I would not be concerned about that issue, but always try to keep things natural.