Click the timestamp for the comment, then click "favorite", then set a reminder in your calendar to check your favorited comments (link in your profile).
Can Siri work with whats in your copy/paste cache?
What do you mean by “copy/paste cache”? If you mean the clipboard history, there’s no such thing on macOS. If you mean the clipboard (= the last thing you copied), Siri can work with the Shortcuts app, which itself can read the clipboard.
I mean like "create a reminder to check link from my clipboard tomorrow"