Behavior in 16.04: Triple-click is middle click (This is an assumption, I can't be certain it was actually middle clicking, but the behavior was consistent with middle clicking) and opens link in new background tab in Firefox. Switcher was/is tiny and looks like shit, but works fine.
Behavior after upgrade to 16.10: Double Triple-Click (but interestingly not a single triple-click, nor a double double-click, nor a double single-click) brings up a very nice looking Switcher I would love to use with alt+tab. It looks great. It's not tiny and doesn't look like shit. It would be wonderful if my alt-tabbing used this switcher, because it's large enough to be visible, the background color is in keeping with Ubuntu's theme and matches the dock.
I would also very much like Triple-Click to go back to being middle click. I can't find anywhere to set this, and it's sad because I can't open links in new background tab in Firefox without that old functionality.
11/7: within the past couple days, I've noticed sometimes my pages are huge or small text. Ctrl + 0 puts zoom back to original. However, today I realized double-clicking (left click) is cycling font size between bigger, smaller, and original zoom. What causes this? Can I turn it off? I mention it because it may be related to these strange changes in triple-click behavior in firefox.
12/9: within the past 2 days, I can triple-click in firefox again. However, I have to be very careful with the right-most finger. It has to be in a very small area in the top right corner of the trackpad, or nothing happens.
1/12: Reinstalled 16.10 because old account would boot me out immediately after login. No tiny switcher, but still getting normal switcher on double triple-click, and still can't triple-click to open links in new tab in Firefox. I can middle click on a mouse, so this suggest that for some reason, triple-click on trackpad is NOT emulating middle click. FOUND SOLUTION: https://www.reddit.com/r/Ubuntu/comments/5807p9/tip_for_ubuntu_1610_use_dconfeditor_to_allow_you/
Does anyone know where/why double triple-click is opening switcher??