Jquery $. Ajax $. Post submit question

Test version jquery 1.5.2 jquery-1.6.1.min two versions of the same problem

One function of the project is that when the user clicks a button to bring up a user-related content, click Submit hidden layer, And the textarea input content is displayed in the DIV to show whether the line feed is displayed, so the replacement is used.

Replace ("\ n \ r", "<br/>"). Replace ("\ n", "<br/> ")

If you press enter to enter the content, you cannot submit the content. If you do not press enter to directly enter the content, you can submit the content normally.

Originally, it was submitted <br/>

I don't know if it's a bug.