I'm going to be starting something that's like giphy/imgur/gfycat etc. Is using disqus fine? Or would that negatively impact the 'value' of my start up? I'd like to hear ideas/thoughts/opinions on this as I googled and googled but not one seems to be able to answer this question.
Personally I dislike disqus. I guess there's nothing wrong with it, but if you have a kind of service users will need to register with anyway - why not create your own system that you can customize however you want, and keep your own data, etc, etc?
On the other hand if you are just working on MVP, and comments are not your main value prop, and you just don't want to bother with implementing your own system - sure, whatever, go for it. There's nothing too horrible about disqus, it's fine.
I have used disqus in the past and I would say, go for it!
Pros and cons:
+ Highly customizable
+ Loads of moderation options(whitelists, blacklists)
+ Active community
+ Easy to use admin tools
- Seems to load slowly sometimes
Also, the most compelling reason for using it is that you don't need to waste time coding your own commenting system. In the future if you decide to make a commenting system of your own, you can always export comments from disqus.
If you're worried about "owning" the data/community, you could host your own discourse (http://www.discourse.org/) instance and use their embed feature (http://eviltrout.com/2014/01/22/embedding-discourse.html).
Embedding is sadly missing inline commenting, though.