If it's their original thought, or I'm including their comment on the thing they shared, then I include the username.
If they've just reposted an image with no extra commentary, I only share the image and not where I found it. Since "where I found it" is not the original source, no attribution is necessary imho.
My brother-in-law just got a new computer and was excited that he again has a device functional enough to play Stardew, so we just started a new farm. This is the third farm I've played with him and we've never yet made it to Winter year 1 (together) as differing schedules always eventually get in the way. Going back to the beginning is grindy, but also a nice change of pace.