@leocg Thanks for your response. To use any online service almost always requires a "password", thus, by definition, the htpc would have "sensitive" content in the form. The question is whether the access to the "sensitive" content is available to any user or just a select few (administrators). A password to block settings makes the most sense. An alternative is to not use a web browser as an htpc interface, but it's the power that an web browser can supply that makes it the most useful interface compared to something like plex or kodi. A web browser is an all-in-one solution for all media types from movies, live tv, news articles, music, games, etc. A Smart TV/Roku can do some things a web browser can, but a web browser can do almost everything in comparison and usually far better.
Add the power of Windows too and you can now have an htpc with PC games, Xbox streaming, Game console emulators etc. A password to lock access to the Password Manager just makes much more sense than to limit the system.

Create password or pin to lock your device.
When you go to Passwords in Opera it will ask for lock credential.
Enter them and you will then be able to see any of your passwords by simply clicking on the Eye to the right of dots ( invisible password.

@didad38 And......... why don't you try any other site to see if there's a problem with it? There are sites which have Javascript code that clears the fields.

@opzvaranka Yes, but I don't understand why Opera has to handle in this way and not via the Google autofill service as opera mini and all the other browsers do?