Well, the global "figures" are as follows:
a double click highlights the word, a triple click highlights the paragraph.
I mean if even considered, it should definitely be very optional.
Psst: in Opera Presto, triple click highlights the sentence, quadruple click highlights the paragraph :sherlock:
If you have "Show advanced settings" checked in the Browser settings, you should have an option in the User Interface settings to "Disable tab bar's top spacing when browser window is maximised." Try unchecking that and see if that gives you back something to grab at the very top of the screen.
You should be able to grab it even as it is now by clicking between the tab menu and minimise icons on the right hand side, but I appreciate that's not very quick and easy!