Opera has placed the "close other tabs" feature right below the "close tab" feature. That's as dangerous as placing a nuclear warhead launch button right beside the light switch in your room. These features being beside each other makes it very likely that one ends up closing all other tabs instead of closing the one tab that one intends to close. This is made worse by the fact that Opera does not have a functioning way to recover accidentally closed tabs; there's no clear list of tabs that were previously open, no way to easily get them back with a click of a button.
So please, hide the "close other tabs" function so that it's far away from the "close tab" function. I'm sure the former function is sometimes useful to some people, but not so useful that it needs to be visible all the time, especially right beneath the "close tab" function. The risk for a mis-click is far too big.
An other option is to add an "undo close other tabs" function, so that in case one accidentally closes them all, with a click of a button one can have them all back. An alternative to this, yet a less practical one, is that you add a warning window which pops up any time one tries to "close other tabs". This shouldn't be difficult since you've already given the user the option to choose if a warning window pops up when one is trying to close Opera.
A third option is that you simply introduce the feature which people have been wanting for years: a clear, easy-to-read list of the previous tabs that were open before they were closed. The "Last Session" and "Last Tabs" files in the "Opera Stable" folder are no good. They are a jumble of symbols and letters which one has to spend hours interpreting to find the web addresses in them, and even after all that work one doesn't really trust that all the addresses for the tabs one accidentally closed are in these files.
The "history" tab is also useless because it only displays the most recent tabs that have been open. If one accidentally clicks "close other tabs" in a window with several tabs that have been open for months, these old tabs will not be in the page history.
I'm a big fan of the "warn on quitting Opera with multiple tabs open" function. It has saved me several times already. But the fact that one can lose all but one of the tabs that are open, just because one accidentally clicks "close other tabs" instead of "close tab", and there's no way to reverse this with an undo function, is really infuriating.
Half an hour ago I lost around 60 important tabs that way. A sizeable number of them were so old that I can't find them in the History list. The "Reopen last closed tab" only opened around 15 of them, and they were the newer tabs. Now I will have to start sifting through the "Last Tabs" file to see if I can find the addresses I lost. Not something one wants to do when busy with other more important things.