There is not a chat function or auction house function in the game, so the rcr (rare card report) and the current leaderboards are where people go to list cards for buy/sale/trade. It is NOT considered bad form to advertise on the walls of the people who are currently listed on the rare card report. When you pull a 5* 6* or 7* card you will be listed on the rcr for some period of time - however long it takes for three more people to pull high cards. What you experienced was just a temporary spamming while you were on the rcr.
After you play the game a while, you won't mind this anymore. Many people are refreshing the rcr regularly to see current listings. If you are lucky enough to get a good pull, you don't need to refresh the rcr, just look at your own wall. Convenient! Or, ignore your wall for a while and spend quality time with your lovely new card
Note: Many of us, however, do consider it bad form to advertise on random people's walls who are not listed in the rcr or on the leaderboard. (I only post an ad on non-rcr / non-leader walls if someone does it to me first. And if you do, at least please send me a brave for f* sake.)