If you see someone sitting by themselves, say hello. Let them know they are seen. Ask them how their day is going. Recognize their humanity.
We tend to live according to our own comfort’s but keep this quote in mind (to my female readers, I apologize for its male-centricity): “A gentleman is someone who holds the comfort of other people above their own.”
Goodness can manifest as social glue and inclusion through curiosity. Reach out so they fit in. It makes a difference.