I know I already don’t like compliments but I especially don’t like compliments I can’t do anything with. “Nice pen” what am I supposed to say? “Thanks I paid money for it?”
When someone is complimenting an owned item, a few things you can go with are "thanks! I got it at [store]!" or "yes, isn't it cool? I got it on a great deal!" or "thank you! I found this gem at a thrift store/it used to belong to x/I inherited it from x". Even if it's some story you think is inconsequential, that's not really the point, the point is small talk, which an inconsequential story can provide
I experienced something like this just yesterday at work, funny enough also involving a pen. I signed a form to change my hours and handed my boss the pen, and as she signed it she said, “Oh my god, your pen is so nice.” I laughed and said, “Thanks. I’ve been using the same kind for years because it’s a simple design and comfortable.” She was like, “That’s so cool. When you find something you like, you stick with it.”