Commenting on videos is a feature that has been around for a long time, but sometimes comments can get taken out of context because it can be unclear as to at which point in the video the comment is directed at. However it seems that Dropbox is changing that by letting users comment on videos at specific times.
This means in a video that you’ve shared, maybe for an advertisement or a presentation, other people collaborating on the project can comment at specific times in the video to leave feedback and suggestions. This will also work with audio files shared on Dropbox. Users who leave comments can also tag other users with the “@” tag.
This is similar to other platforms such as Soundcloud where users can comment on specific parts of a song. To a certain extent, other platforms such as YouTube and Facebook have similar features, except that they only work for live videos where you can see which comment was made at which point in the video. It is unclear why this isn’t becoming a mainstream feature as it does seem pretty useful.