If you don't copy/paste a link from any email within a year you end up falling off the "active users" segment and we stop wasting our time sending you emails. For text-only users (which we seem to have a few who have "clicks" but no "opens"). The particular system I work with is actually slightly more sophisticated and considers usage from a lot of channels (push message consumption, email opens and clicks, app usage, alexa usage, bot interactions, and website usage). If you don't do any of those things you fall into less and less frequent push/email interactions until we stop bothering with routine newsletter/updates messages except for an occasional "please come back"-style campaign.
"Copy/paste" here means "Copy the URL, paste it into the address field of a Web user-agent program, and initiate navigation to that URL in that Web user-agent program".
I suspect the phrasing was used since the discussion is about text-only email and, this being Hacker News, someone might have nit-picked that they view plaintext emails in a mail user agent program which does not scan for strings matching the format of a URL and offer a direct way to click on them or otherwise trigger automated opening of them in a Web user-agent program, and so the person who wrote "copy/paste" had to avoid saying "click on the link".
Copy pasting into the browser to view the link triggers this, just copying doesn't. If I understood the previous comment correctly, the author copies links into the browser instead of clicking them (since they aren't clickable links).
