EDIT: Guys I found a work around for the current issue. I don't know why I'm having such a hard time since 7.0 in copying double spaces, but now I can copy to notepad then copy to sigil and it'll copy them just fine.
Still though, it would be nice if you guys fixed whatever issue is going on. tyvm 
original post below:
HI.
I have to say that I love sigil but since 7.0 you guys made a change to the system that turns all double spaces after a period into a single space when I copy and paste a file or portions of a file into sigil's book view. See, in previous versions, if you copied and pasted a work with double spaces, sigil would automatically enter the double space code: " ". Sigil no longer does this. You can still add double spaces manually or find and add, but it doesn't do it automatically.
Unfortunately, because of this change, I cannot use the current versions of sigil. The reason for that is that it is imperative that I have double spacing after periods without having to go through and manually add them all. In previous versions I was able to copy and paste these double spaces just fine without sigil "auto correcting it" to single space after a period. In fact, there are many areas where I need multiple spaces strung together in my written works.
If this is an option I can turn on and off, please inform me, otherwise I have to downgrade. That's because for me to go through and manually or even search and find all periods and spaces in my works and replace them with period and double space would take more time and effort than it is worth. I am making a formal request for you to restore the "Copy Paste, Double Space Encoding" to the current sigil version.
I sincerely hope this was not your attempt to force us to use Chicago or MLA standards, because those standards are wonky and constantly changing. They also are not true standards as many publishers reject them due to MLA and Chicago's numerous rule inaccuracies.
EDIT: minor correction - from some programs it's working, from others it's not.