Another very low-risk option is to cut and paste your favorite quote(s) from an entry and mark it as such. I get that one fairly often on fanfic and it's fun to see what snagged someone's attention.

I do do this occasionally for fics (along with simply hearts, smiley faces, and 'this was great'/'I loved this'), but for journal entries I do like to add something of substance to a conversation.

That rock sounds super cool... my dad was very into history/archeology and the coolest rock tool he had was a piece of Icelandic spar for finding the sun on cloudy days :)