Mercury is considered the planet of communication, intelligence, and commerce. A strong Mercury in one's birth chart is generally seen as a positive influence, indicating good communication skills, a sharp intellect, and success in business or trade. However, there are some traditional beliefs that suggest certain items should not be donated when Mercury is strong in a person's birth chart.

One such belief is that donating pens when Mercury is powerful can weaken its positive influence. The reasoning behind this is that pens are associated with writing and communication, which are also ruled by Mercury. Donating pens is thought to be like giving away some of Mercury's positive energy, potentially leading to difficulties in communication or a decline in intellectual abilities.

It's important to note that these are traditional beliefs and not scientifically proven. Many astrologers believe that the overall effect of a strong Mercury is positive and that donating pens would not significantly alter its influence. Additionally, other astrological factors and the overall planetary alignment in a person's birth chart should be considered before making any conclusions about the strength of Mercury or the appropriateness of donating certain items.