User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Firefox/52.0 Build ID: 20170607123825 Steps to reproduce: I paste text & create a hyperlink out of it. Actual results: I try to stop typing formatted text, on that same line, but Thunderbird ignores any attempt to change the text color, deactivate the underline tool, and/or discontinue text link to URL. Expected results: Thunderbird should discontinue the hyperlink formatting when: a. When [CTRL]+[SHIFT]+[Y] is pressed. b. When underline is deactivated (but still allow for non-underlined links). c. When part of the link's display text is highlighted and the URL is removed from "Insert --> Link... Ctrl+K" Link Properties --> Link Location text field.

Operating System: Windows 8.1 (64-bit) Thunderbird: 52.2.0 (32-bit) Link to a video demonstrating the issue: https://drive.google.com/file/d/0B1vf0VJVd6U0c0RlLWVodnJSVkE/view?usp=sharing

C. should probably read: "[Discontinue formatting] the part of the link's display-text, that's highlighted, if/when the URL is removed from the Link Properties -> Link Location text-field."

I think you're complaining about a variation of bug 1273655. The link text gets continued under certain circumstances. Of course any formatting applied to that link text is ignored. It's a Mozilla core bug since it can be reproduced in Firefox alone using the example given in bug 1273655.