Did you ever get an anwwer to this?
I am having the same problem on a fresh install of WordPress 4.4.2 with MailPoet
BTW, the code above had the ! on the wrong side of important so it should look like
#commentform label.wysija-box-after-comment {
width: 100% !important;
}
Which I tried but to no avail.
I also tried hard-coding the width to a fixed pixel width of 1000px but it made no difference.
I assume most people do not change the text for the label of the Subscribe button so never see the label wrap like you do if you have a longer text string.
FYI, just to trouble-shoot, I changed my label so it had not spaces in it so it read
“Please_add_me_to_your_mailing_list.” (without the quotes)
and the whole line started under the checkbox and broke after the i in mail.
I then removed characters until the first unbroken string did NOT wrap, and I had to cut back to 6 characters in the label (Please) to get it to stay on the line beside the checkbox. After that, the remainder wrapped.
So, the issue has struck at least a few of us. It may be present for more but they don’t know about it.
Any ideas?