As stated earlier, the question of who counts as a companion is basically the oldest "fight" in fandom, and it never gets resolved. So, having allowed the discussion to proceed for a number of days, I'm just going to close this discussion the way I've closed the rest: there is no right answer to who counts as a companion.
More broadly, arguing over who and who isn't a companion is counter-productive. It might "fun" in a "ain't it great to be a part of DW fandom" sort of a way. But it's wasting time we could be using to edit about things that are much more cut and dried. And, worse, it creates these little edit wars, which also are against policy. (Remember, guys, when you edit pages that are currently under discussion, you violate T:BOUND and risk blocking.)
Worse, it really doesn't matter. These are navboxes, not articles. It doesn't matter if they contain information that is dubious, so long as it's reasonably defensible.
So, again, we're basically at this point: we can't agree who counts as a companion, so who decides? By default, the answer is admin. Now, I don't like that answer. I'd rather find a way for the community to decide. But it is just not going to happen. Not on this issue. Not in this fandom.
So the best I can offer you is an evolved stance that is tempered by the discussions we've had over the years. In other words, I've read the comments of everyone who's ever participated in this debate, and to one extent or other, their thoughts are incorporated into the way companions are chosen for these navboxes.
Mini-mitch once proposed:
- I think a companion is a person who travels with the Doctor on more than one adventure. Unless the BBC state that they are companions.
And frankly that's pretty much it. But because I like lists and a little bit of amplification, I'd throw in this.
- As long as the answer to one of the following is "yes", the character in question is likely a companion:
- Is there a press announcement that introduces their actor to the world as a "companion", "assistant", "regular" or "semi-regular"?
- If the character isn't on television, does the publishing company refer to them as a "companion" or "assistant"?
- Do their actor's names appear before the title of the programme on television, and are they not also a main antagonist?
- Do they occupy a narrative space equivalent to Wilf or Christina de Souza in a non-televised story in which no other, more obvious, companion also appears?
- Do they travel in the TARDIS in a single story when there's no other, more obvious companion in the story?
- Does the Doctor refer to them as his companion, assistant or maybe even friend during the course of the story, particularly, but not exclusively, when there is no other, more obvious companion in the story?
- Does any reference work refer to them as a companion or assistant?
- Were they under contract to appear as a regular or semi-regular in at least one series on TV, and are they protagonists?
- If their actor's name is above the credits, did their character receive and accept an invitation from the Doctor to travel in the TARDIS?
And, really, that's what Mini-mitch was saying back in 2011, just much more economically than me. :)
Now, that said, I'm going to additionally move to end all this. From this point, the navboxes are off limits to all but admin. As we can see upthread, leaving them open to editing makes people come dangerously close to violating T:NO WARS, and it's just not worth it. I mean, we could honestly not have these templates at all, and the pages wouldn't be much the poorer for them. So, to stop this issue from continuing on into August and potentially ruining the start of series 8 for me and the rest of the admin team, all those "companions of" templates are now locked.