If you read the first page of the thread you just posted this in, there are several good explanations of why the system is programmed the way it is, including one by RawTop (the site owner, who makes the rules).
Here's the TL;DR:
It's not just the number of comments a day. Other parameters (including the responses to your comments) count, too. So making "me, too" posts will (probably) count for less than will constructive contributions to the discussion.
The exact details are not disclosed TO ANYONE (including the moderators), in order to prevent spammers from spoofing the system, and for the reason hazarded by @TheSRQDude.
The stated and intended purpose of the site is to be a discussion forum, NOT "to message other people". There are lots and lots of sites that do that already (BBRT is probably the best for people who enjoy BZ, despite its drawbacks).
It really doesn't take that long to get out of "New Member jail". It just feels like it. There is at least one Junior Member (the second privilege level) who has barely been here more than three months, and whose total number of posts is less than 50.