means absolutely nothing to me without the contextual menu that disappears after firefox closes.

5 star if they fix this issue. The shortcut Alt+p doesn't work the same way as the context menu and therefore can't be considered a replacement. The shortcut has to read the entirety of what was selected before you can make it read something else unlike the context menu button who interrupts the current text being read to start the new one you just selected.
The way I use this addon most of the time is to research subjects I'm unfamiliar with. I make it read while I keep looking at other stuff I'm researching. Most of the time, I understand what I was looking for mid read and I'm ready to TTS the next thing and it's already highlighted so I just right click to open the menu and make it read the next part I'm interested in which it does immediately by interrupting the previous text being read. The shortcut doesn't do that. If it's already reading something and I highlight something else and press alt+p, it just stops reading. If I press it again, it resumes the read of the previous text not the new highlighted one.
Could be solved by adding another shortcut like Alt+n (for next or new) to fix what's described above.

Another problem I have with this addon is that if you use more than one language, the voices options and choices become pretty much useless. In my case I want the addon to read both English and French texts sometimes. The only way to do this is to choose the Auto select option in the voice choices. Doing so give you a random voices for both languages and you have no say in what voice you want for each language. They seem to be chosen randomly as far as I can tell. The English male voice I got is one I hate and can't stand listening to, same for the french female voice I randomly got but that one is a little less annoying. If I select any other voice instead of the auto select option, then I'm stuck being only able to read one language because that same voice I chose butchers the other language it's not designed to read. I could go to the options and select the voice I want each time I switch between languages but who the hell would wanna do that?