Comments now has three tabs — Comments, Mentions and Reviews — on the web and in the app. All posts is gone: the Comments tab lists every post people commented on, from all your accounts, the ones with new comments first, with their number.
One row of two menus filters every tab. All accounts ▾ holds your channels too — All Instagram, All TikTok, All Facebook — and each account with its @handle; past six accounts it has a search. Choose one account to see every post it has. The second menu narrows the tab: All comments · New · No reply in Comments, Last 7 / 30 / 90 days in Mentions, All reviews · Not answered in Reviews.
Mentions splits in two. Mentions lists the comments and captions on other people's posts that name your accounts, each with Reply and Mark as seen. Tagged shows the posts that tag your accounts: Instagram does not let apps answer a photo tag, so each opens on its platform. Older posts now show their picture.