[Why] do people put things in brackets in their WSO thread title?

To stand out. Other sales threads may be selling similar products; or their titles may start with similar words; this separates it from other threads, or makes a person look at it first.

I will be honest, it made me notice this thread first when I went back into the main marketing forum; it stood out. Text, upon, text, upon text can be hard to distinguish and read sometimes.

It's basically a heading within a heading. People used to put tons of characters and funny looking things, in the past. That was banned, but the point of doing that too, was to stand out.

Have you ever sort of noticed that the brackets for you to read what is inside, even more so than just a plain heading? The brackets, in natural English, are a sort of secret whisper, almost. They tell something about something else, and people, being as nosy as they are, always want to know what that something is.

Think of it like someone whispering to someone else... with their hands blocking your vision, so you can't see what they are saying. Who doesn't sit there trying to figure it out anyway? Those brackets remind me of that, only you are the one, who the secret is being told to.

Odd analogy, but it really does remind me of that principle.

A sample Title from back in the day (400 pages in):

$$$ •••••►►► “Water For Gas” PLR Package ◄◄◄•••••• Make $$$ Even After Being Google Slapped

Again, if you could jump up and down on the street with a sign, and get people to pick you over 50 other people doing the same thing; you may have to start doing some back flips or dancing to stand out at that point. Same principal applies here... there is only so much pizzaz your text can have, when it is limited to a certain font, a certain color...and certain character codes (the above codes are no longer allowed...circles and arrows, and black block text).

To stand out from the crowd and make key words such as 'free' stand out.
Though as you said a lot of people are now doing it so it's not as effective as it was when people first started doing it.

Readability, and differentiation

It stands out from the rest. When I send email ads I always use brackets.

Trying to call attention to a certain word or phrase would be my guess.

It's one of the few non-alphanumeric characters allowed in the title! Furthermore, it allows you to stress a key attribute of your product or service.

Interestingly enough, I've found it more effective to put the bracketed attribute at the END and not the beginning.