User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

1. Write a message
2. Add a URL (or other words)
3. Add a hypertext link to this URL
4. Continue writing after the link

Actual results:

The letters and words written after the link was created on the same row get into the hypertext link (blue-colored, underlined, and in the link content (above "Link Location" on link creation window)

Expected results:

I think we specify just the words / URL that need to be in the hypertext link, so the next written chars should not belong to the link, to my point of view.

This little disagreement can be avoid by simply writing the entire message before adding any hypertext link, but that's annoying.

Hope this can help you to improve Thunderbird

(v 68.8.0 (64-bit))

I can't reproduce using Thunderbird 68.8.0 on Ubuntu 18.04.4 LTS.

Opened the composition window.
Typed some text.
Selected Insert > Link.
Typed some text into the "Enter text..." field.
Pasted a web page location in the "Link Location field.
Pressed the Space bar and continued typing in regular text.
Continues in regular text after the link even if I don't press the Space bar.

Indeed, it works as expected when you do so.
But the (little) bug still happens when you start by writing the words / url of the link, then selecting the interesting part of the text and launch the hypertext link creator, contrary to launching this utility at first before writing content.
(Thanks for this tip, it seems to work better this way...)
I hope my explanation are enough clear.

(In reply to samuel.ortion from comment #2)

I hope my explanation are enough clear.

Thank you samuel for reporting this! Your description is correct, and I'd agree it's a bug. Confirming. Age-old little annoyance: Duplicate of bug 554264. Nobody wants to touch editor bugs... :-/ For added clarity, pls include every little step like 2b) select 'linktext' in message body.

Some possible workarounds:

• Create link from scratch using Ctrl+K to enter link text and URL.
• Press Ctrl+End when you're done with your link at the end of message body text (which is a bit easier than remembering Ctrl+Shift+K to finish the link)
• Type another word or even a space after your linktext and make sure not to select the space when adding the URL, then press navigation keys to move cursor to the right of that space before you continue writing. (I hate that new behaviour where double-click selects the word and trailing spaces...)
• Note that for an existing link between other words, it makes a difference if you reach the "corners" of the link from outside or inside using cursor keys. After navigation coming from inside linktext, it will extend the link text. From outside, it'll create regular text. Try it!