How to mass export files from chatter feed and chatter comments.I looked into the reviews of file exporter app but it looks like it is not supporting chatter attachments.Is there any other way to achieve this?
You can use the API to accomplish part of this. For files that are attached to feed items, you can query the FeedItem SObject for ContentData where the Type = ContentPost.
Unfortunately, files attached to comments aren't supported in the SObject API. They're supported in the Chatter REST API and Chatter in Apex, but you wouldn't be able to do a mass export because those APIs can only run as the current, logged-in user. They're not data APIs.