I had tested this example.

 

But in my case there is a little bit different.

  

When the CuteEditor is in Normal Mode , the characters count was less than 4000

When the CuteEditor is in HTML Mode , the characters count was more than 4000 

   When characters length (HTML Mode) was too big for eg 4100 , then the prompt did appear saying the characters exceed the limit in both "Normal" and "HTML" mode

   However, when  the length was reduced to 4065 , and I submit the query. There are 2 scenerio

    1.) When CuteEditor in Normal Mode (With HTML text = 4065)  , No prompt is given.

    2.) When CuteEditor is in Html Mode , then the prompt appeared.