HTC didn't write the forum software. BUT.... SMF does allow you to change that setting, but there is no reason to do so.
It would be impractical, causing far more work for the HTC team.
That 30 second restraint is there because aside from us, there are thousands of spammers out there writing code for multiple spam postings. They log in, and then PM 100 members at a time with an advertisment for black market Rolex's.
Do you run a forum? I do. You wouldn't believe how many ways those bums try and break in. Some of these "silly" rules are here for all of our protection.
And besides...............
A thread with 4 replies should take about 30 seconds to read........ Have a little respect for the people before you.