Is it unacceptable to comment on someone else's phone conversations that you can't help but overhear?

sometimes my coworker who sits in a cubicle across from me will comment on something she overheard me say on the phone, or ask me about something she heard me discuss. i know she can’t help but overhear my conversation. i will also comment on another coworker’s calls, but only if it’s business (like i will tease her about the things she said to the customer, but i will not comment if it seems to be a personal call). i am wondering if it’s improper or unacceptable to comment or ask about something we can’t help but overhear, but yet actually does not concern us at all?