It starts to freeze up the browser when the character count goes over 32,000 - It's like this html text box isn't handling string concatenation well.   If I was to paste in 52,000 characters in this box it will hang it for like 15 minutes.. 

 

Now if I pasted 52,000 characters in this tool: http://www.charactercountonline.com/

 

It accepts it without an issue and counts it fast. 

 

So there is definitely an issue with how strings are being handled.