jotto wrote:
....
> unless session[:countcomment] !=nil
>   session[:countcomment] = 0.to_i
> end

I would avoid the double negative:
  session[:countcomment] = 0.to_i if session[:countcomment].nil?
...

> if session[:countcomment].to_i > 1.to_i
>   if thiscomment.save
>     session[:countcomment] = session[:countcomment].to_i + 1.to_i
>     render some text
>   end
> else
>   render_text "too many posts"
> end

The logic here is saving the comment if the count is greater than 1?
The opposite of what you want.

Also, why all the to_i calls?  

Cheers