True that too many categories leads to compromise/confusion. I don't demand that new categories be installed, just any way to locate cars with specific details. The comments field is very useful, if it could be used in conjunction with the make/model fields. Currently, they are independent (either/or). It is not necessary to strive for a seamless search capability such that a used-car website would have (year/make/model/style/doors/color/seat config/accessories/etc).
This is still an irreplaceable website and community.

Actually we even have too much categories now. Though that it can be useful for doing searches (the only reason why there are such categories)

I also don't see the point in all the categories. I like to know at least year and make - model is nice but not really necessary as I can look up all the other stuff.

I don't think that this site can be an exhaustive enclycopedia of car information and it seems that is where we are headed.

In addition, I continue to think that misinformation is worse than no information.

I still do not see the interest of that "better categorization", knowing that many will be wrongly listed (like currently: as I mentioned above there are categories with common errors).
Going so far in the details, 2-door and 4-door sedan could also be separated; 3-door and 5-door hatchback too, etc.
But that would not provide much useful info.

Better categorization? In case we have two versions of a given model (common for American cars until 1970s and Japanese sedans until 1990s) it is good to categorize them as such.

Hardtop coupe is a sensible extension of the category scheme.

I do not see what is the interest of separating them. And what about hardtop coupés?

Again, what's the problem with hardtops? They are not any harder to distniguish than a wagon from a hatchback from a sedan (esp. now that we have no "liftback" category). It is more visible than whether the tailgate includes the rear windscreen (i.e. I could easily forgive someone not familiar for mistaking an Octavia for a sedan).

I agree, there are so many categories with fuzzy boundaries that it is difficult to always get it right. The result is that we have misinformation on the site and that is not good.

It is fairly clear whether a vehicle is a sedan or hardtop. Either it has a B-pillar or not!

Well, why add a field for that? There is already the extra info field which is made for info like that... Or you mean split the sedans in two categories rather than just "sedan"? I do not think that it is a good idea, we have already so much miscategorized vehicles between sedan/coupé, sedan/hatchback, wagon/mpv/hatchback, etc.