In what case does it not work?
I copy text normally by Ctrl+C or from context menu after right click. Stripping is done later during pasting in Obsidian either by “Paste as text” from context menu or by Ctrl+Shift+V.
For me in Windows 7 it works when copying an article from internet browser (Chrome) and when copying text from preview mode within Obsidian. I did not test other cases yet.
Nothing is stripped when copying within Obsidian from edit mode because all characters are part of content there, even when they displayed as formatted by CSS (unlike requested in Edit in plaintext mode which however can be achieved also by custom CSS overwriting the default one.)