I've seen at least one reference to:
Code:
<title>Rich text editor, editor, press ALT 0 for help.</title>
magically appearing in Code View in this thread, but didn't see where the issue was formally acknowledged.
To consistently recreate the issue (I'm sure there are other ways):
1) Open Sigil 0.5.902 (brand-new empty document)
2) Switch to Code View of "Section0001.xhtml" (note the "<title></title>")
3) Delete the "<p> </p>" line in Code View
4) Switch to Book View
5) Type some text
6) Switch to Code View and note "<title>Rich text editor, editor, press ALT 0 for help.</title>"
The text itself comes from a default setting in the language files (en.js) for CKEdit. Thinking it might be connected to the empty title tags... I tried entering a title (in step 2 of the above recreation steps), but no dice. The text I entered is still replaced by "<title>Rich text editor, editor, press ALT 0 for help.</title>" if you complete the steps.
Tested on Windows and Linux. Seems like it may be a common thing since I've found evidence of a few live websites with that same distinct title.