To be on the safe side, I think newbies should maintain a 30 mins gap post, at least. Even when the next post they want to comment on is an easy read or just a post or two in a thread before them. There shouldn't be a haste to posting. As high ranked members, I guess anything that's not a minute interval isn't frowned on. Perhaps the misconception could be that high ranked users are viewed as being constructive in their posts. Posting within a short duration could be viewed as burst posting for some while for others it could be judged as spamming. It depends, I think. For me, I try to keep a reasonable gap as that affords me the time to peruse other content on the forum or get something outside the forum within the few minutes of waiting. Anyone who's genuinely reading before posting won't be posting at close intervals. A few years ago, there were campaign managers who specified posting gap in their campaigns. I think it used to be 30 mins interval.