Again, @amosbatto great informative post. Suggestion: make it a poll and come back to it in five years or so…? We’ll see how wro… right we were 
Regarding @maximilian’s reply, I think it’s absolutely crucial that there is an ecosystem of manufacturers that have Linux systems available. It’s not just about app ecosystem. Choices are needed but also, different approaches bring new ideas - development. Some will work, others will not. Not all ideas will or should or need be adopted, but they may be a stepping stone at some later point.
I noticed that in the original post it was actually left blank, which are/is the L5 features. (edit: sorry, they were hidden within the list) Got me thinking. We have the lists of course (as vague as the features were in the beginning), but most of those are not especially new. Most are “just” made in a special way - open, verifiable. Not to take anything away from L5 or anyone else, but as there have already been Linux phones and projects (Maemo included, and Ubuntu worked etc.), I’d see Purism - and don’t kill me here - closer to early Apple than an actual innovator, as they took known stuff and developed and polished the whole experience a couple of notches above what had been previously seen (and remember, the first tries weren’t what they became - and even still, as most have same or better tech features, the experience is not the same).
Thus, I see a possibility that L5 could give some early indication of what a future standard in “owning your phone” could look like. Much like Apple set a path to usability/experience. And in this, I come back to L5 maybe not having a specific feature that may or may not last or get copied. Even the three off-switches themselves may not be that important - those may evolve (there are already examples of variations of those by others) to one, two or four and their functionality change. “Secure” or “FOSS” or “sustainable” have different variations - and overlap - available too. Which is why I chose “owning” as the main “feature” of L5, and agree it is intentionally a bit vague and abstract, concept.
As a side note, it would have been interesting if HTC would have chosen to go fully open (and secure) to counter perception and sanctions. Too bad that they still try to hang on to an old troubling (privacy-wise) market and not cater to a possibly burgeoning new segment. Well, many other things in that whole mess, so not mostly relevant.
Also, I don’t see L5 as only a Linux or FOSS phone, but the aforementioned overlap is also with other manufacturers that cater to secure communications boffins. These are often the early adopters that lay the groundwork for future de facto reguirements. In these scaled situations though, I remind of John Sowa’s “law”: “Whenever a major organization develops a new system as an official standard for X, the primary result is the widespread adoption of some simpler system as a de facto standard for X.” The likely outcome that I see is that, yes, “owning”, “privacy” and “security” will increase but not to the intended level in the larger population. Something will be absorbed to the industry.
Lastly, I think trust is a major factor. If L5’s “features” or concept is to propagate, with the larger masses (or even with many in this group of early adopters), there needs to be authorities, instances and organizations that have endorsed them. Most will not dig deep - they trust. With the Apple example, the “authority” was hipsters that were thought to have “taste and understanding of fresh” (as opposed to previous, more engineer based approach - a simplification for sure). Their example was followed. So, if active and influential groups endorse these features and says they are worth the trouble of learning something new (ROI principle: expected return on invested time/work/resource to make the change), L5’s example has a chance. There is, of course, competition on the field.
All in all, I think L5 is not going to be the most shining spot in history that everybody remembers. It’s not going to be the one that changed industry, even though it seems to have all the right parts. With Apple I’d say it was the next models that really took off. And Purism might not be Apple - it could be Nokia, which had tested touchscreens and other features years earlier but hadn’t gotten it to the needed point. Yes, L5 might be too early for mainstream. But I also think it will push that boundary and move this from “very early adopters” and closer to “early adopters” territory.
(edit to add: Only later we’ll be able to say what was the “main thing” that we identify as the L5 defining feature. One option could be that it will become known for it’s convergence desktop experience - “finally a phone that works as a computer and has support” [edit: “a phone that has enough juice and good enough camera etc. - is not lacking in anything” ]. And all the rest - security and privacy and long lifetime - are more of “bonus features” than the main attraction.)
