There's a very annoying bug when pasting text in a container that already exists. At first it pastes fine, but when I change some properties of the container (for example width), the pasted text is gone and the old text is there again. So I have to paste again, click around to make sure that the pasted text remains, and only then change properties.
Also while pasting, an empty line above and two emty lines below are always pasted, so I have to delete them every time. Very annoying as well.
You can paste text only with CTRL+SHIFT+V. No more unwanted lines or something using that.
Your Issues are probably caused by not pasting from a raw text editor as needed for web design. When you copy from sources like the web, Word, Wordpad, and the like, you will also be copying possible hidden formatting. That's why many times you'll see Bold text when you paste it if the original you copied from had bold. You need to copy the text to a basic text editor like Notepad (windows) Notepad++ (windows) TextEdit (Mac) Notepad (Mac) etc.
Then you copy the text from there to your project and you will most likely not be copying anything other than the raw text itself. Less apt to pick up extra spaces, lack of spaces, extra line breaks, etc.
Ah damn, you're right, raw text doesn't cause extra lines. I had no problems with formatting, so I assumed BSS is clever like that :D
Cmd-Shift-V does nothing by the way, I know it's supposed to strip all formatting from copied text, but it doesn't seem to work in BSS. There's also no command in the menu for this action.
The other bug is unrelated to formatting and still there of course.
The extra lines are probably because it's copying things a little farther up than the end of the line. That happens quite often and once again pasting to a raw text editor will help you not grab those lines as well. This can also be the same for trailing lines that are accidentally copied without realizing it. Does depend on the source being copied from in many cases too.
I've not ever had any issues with things disappearing for quite a while now though so I'm not sure where to send you on that. You may want to contact Support directly. They will most likely want to know if it happens in multiple projects or just one so you should double check to make sure it's not a glitch in your project file which they may also be able to help with if it is.