Hardly

It is a reason not to buy a game, but I doubt many people do so, and it likely isn't a reason why TMS#FE didn't sell well. It likely comes down to being a niche game on the Wii U and being too Japanese/anime-ish. People either didn't know about it, were not interested, or its visual style pushed them away.

Personally, no game has pushed censorship enough to keep me from buying, and the censorship in #FE should not be a reason to pass on buying it, as it is quite an excellent game which censorship doesn't harm it in any sort of way.

If censorship was a reason to not buy games, then I guess Fire Emblem Awakening and Fates should've been failures sales-wise :P

In all seriousness, censorship doesn't really bother me because (if we're talking about Nintendo since it's on this division of discussion thread) it's not really substantial and doesn't significantly affect the overall plot or gameplay for me, personally. And some of these complaints are a bit petty. For example, complaining about Capcom covering R. Mika slapping her ass before doing her Critical Art or not being able to see a crotch shot from Cammy or when IS covered Tharja's ass when she was wearing a swimsuit.

For me, it depends on the censorship. 

If it's minor cosmetic or text change to fit a different region's standards...I couldn't care less. 

If it's a big change that doesn't impact the game as a whole, say like some sexual content being changed...it's a bit touch and go, but usually I don't mind. I have...other outlets for that, and this typically doesn't impact the story. If it does...see below.

If it's a major change that actually impact how the story is told...then I have a serious issue with that. The video below is a good example of this...and something I would never ever support.

On the specific topic of Fire Emblem Fates....I thought it was fine. From what I understand, the censorship was minor, with the only updates being done to remove some bikini costumes I would have never used, make the weird petting minigame slightly less weird...and I think removing some video clips. Of those, the only one that annoys me is the last one...though given what was included anyway, I feel like they probably should have just left it. You can still see cleavage, you can still pet girls, you can still marry your sister. I suppose Nintendo was trying to nudge the game just enough to get under a certain ESRB rating. *shrug*

In the US its fine. Its the european version thats censored.