FL studio is a weird one like that. In anything else if it's into the red on any channel it's immediately audible. In FL Studio you can push it WAAAAAY into the red on any of the inserts but as long as the master is below 0db it's fine. My advice is to try and keep it below 0dbs anyway. That way you get into the habbit of not doing it on other sequencers. FL studio uses a 32 bit audio engine, so you're not likely to be able to make out the noise difference between a hot and not so hot signal once it's limited on the master channel.