The select tool has changed from being a toggle between two operators to now always do only one task. A always selects everything. De-select is now set to Alt+A (as shown in menus). This gives a consistent way to select/deselect regardless if there was something selected or not.

What you experience is Double-tap A which is an alternative way for power users to quickly de-select. Probably some of those taps were counted as double-tap so that's why it felt weird. This is not advertised in the UI (but it should be in the manual) as it's an unusual way to access a key, the advertised way of doing it is Alt+A like shown in dropdowns and search.

You can bring the 2.7 behavior of A to select/Deselect toggle depending on whether there is a selection, go to User Preferences -> Input -> Select All Toggles.

@Campbell Barton (campbellbarton) I'm not attached to this in particular but I think if used in more places could catch on as a way to run the opposite of certain operators that use Alt, especially those far from Alt in the keyboard (like Alt+H could be H+H). It's unusual but so was right-click selection. If it brings trouble and confusion I'm fine with removing it. But this case in particular was due to expecting 2.7 behavior, not misclicking or so.

I think the double-click A is problematic as well, in its current forum I would not keep it. It seems to have been some compromise, but now that there is a setting to change it, it makes less sense.

If we want to keep something like this, it seems better to make Select All test if all objects are selected, and in that case deselect all. That way you don't have to press the button within a certain amount of time.

Just saw this.

The toggle select in preferences helped a lot thank you very much. If I find anything else, I'll be sure to let you all know.

Thanks again and keep up the great work.