clearing out submitted form

page.replace_html 'blog_entry_comment_body', ''
page.replace_html 'blog_entry_comment_subject', ''

this isn't doing what you think it is doing. it replaces the contents
of tags, not the values. (actually, replace_html will work on a
textarea, but will not on type="text" input)

you want to do something like:

# blog_entry_comment_body => textarea
page << "$('blog_entry_comment_body').value = ''"
# also works
#page.replace_html('blog_entry_comment_body', '')

# blog_entry_comment_subject => input type="text"
page << "$('blog_entry_comment_subject').value = ''"

you are submitting the form via ajax, so therefore the page is not
being 'reloaded' and thus firefox or IE is not auto-filing the forms
for you at this point because you never left the page.

You can also use Collection Proxies in RJS like so :

page.select('div textarea').each do |element|
  element.value=""
end

This takes all of the text areas in a div and replaces the value. You
could also use the div name like so :

page.select('#id_of_textarea_here').each do |element|
  element.value=""
end

So if I had a <textarea id="id_of_textarea_here" ...

That should replace the value.

Hamza