Sorry, but the answer is 'almost' - and it will depend on the social network in question and your role in the community.
Because all social networks work differently in how they allow services like ours to access their data, some of them do not have the ability to 'tell us' about any comment in your community. We may need to 'ask' social networks about new comments in each post, and it means that we will have to limit ourselves on how many posts we track on top of your feed, because making such requests to your old posts will often be unnecessary and we have to follow social network limits for requests. However, the chance that some really old post will get commented is close to zero.
Twitter and YouTube - yes, we will catch all comments in all tweets/videos of the community.
Facebook - for the Pages you manage (have role in them), yes, you will receive all comments, other Pages (you have no rights for) - only top posts as many as shown in your price plan will be tracked.
Instagram - yes, IF your account is switched to business AND your FB profile has role in the Page this account is linked for - yes, you will receive all comments. We don't yet support third-party Instagram accounts (where you have no rights for) or your Instagram account you haven't switched to business so far.
VKontakte - yes, for your community, if you set up additional callback tracking mechanism which allows to catch everything. For other communities you don't have rights for - only top posts as many as shown in your price plan will be tracked.
Odnoklassniki - no, only top posts as many as shown in your price plan will be tracked.