Comment length obscures 'submit' button

I have been using Discuz  for some time and have found it to be the best of the bunch except for a couple of small annoyances.

I am an Administrator on theunituk.org.uk and am running the latest version of Wordpress on the Codium Grid theme which does not normally limit the length of a 'Post' page.  However, when typing in a long comment, as the comment box increases in size, it pushes the 'submit' button down and off of the existing page limit and so whenever I wish to submit a long reply, I have to put in a couple of words and submit the document in order to register it and then go into my Admin facility to finish it.

I also find that the reply button does not work for me and, again, have to use my Admin facility to reply.  I know that the reply facility works for my correspondents.  I have deleted all other comment plugins but to no avail.  I do use the comment Leader Board plugin and it works well.

Incidentally, I noticed in another post that there was a reference to Jatpack comments.  Jetpack does not have a comments facility and I cannot find any plugins with the name Jatpack.  Was this a typo (though it occurred twice) in the other forum post?