"don't think: your ideas aren't good enough"

There's a difference between "Don't think your ideas aren't good enough" and "Don't think: your ideas aren't good enough". The first could have "that" after the "think" and sounds very sympathetic. The second is telling you not to think and that your ideas are bad.

There are lots of websites showing the funny side of getting punctuation wrong:

10 Hilarious Examples Of How Punctuation Makes A Big Difference

Here's a particularly famous example:

“Let's eat, grandpa” versus “Let's eat grandpa”

Here's another:

It’s not just the addition or lack of commas that can change meaning. This example shows how the placement of punctuation, such as full stops/periods, commas, and question marks, can turn something that seems loving and innocent into something more sinister:

Dear John:

I want a man who knows what love is all about.

You are generous, kind, thoughtful.

People who are not like you admit to being useless and inferior.

You have ruined me for other men.

I yearn for you.

I have no feelings whatsoever when we’re apart.

I can be forever happy.

Will you let me be yours?

Gloria

Now let’s see how those same words read with the punctuation in different places:

Dear John:

I want a man who knows what love is.

All about you are generous, kind, thoughtful people, who are not like you.

Admit to being useless and inferior.

You have ruined me.

For other men, I yearn.

For you, I have no feelings whatsoever.

When we’re apart, I can be forever happy.

Will you let me be?

Yours,

Gloria

A light-hearted look at how punctuation can change meaning | CyberText Newsletter

But, seriously, punctuation is useful:

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9 Funny Punctuation Mistakes You Don't Want to Make! - YouTube

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