There're still people like me who leaves gaps in their posting time even if it's on different thread not just to be considered a spam maybe it's just some sort of hobby or maybe they just wanted their account latest/past posts to be clean just like in my case. 
If the person posts in a natural way, in response to some subject, sharing information or expressing his personal opinion about something, it is really irrelevant to post too fast in several topics.
Speaking of myself, I can keep up with several subjects at the same time, so it's not difficult for me to comment on two different topics in a short period of time.
It all depends on whether the other users who are participating with you in the topic are active and respond quickly to your post.