The second statement is Feng Shui.
In order to respect the Yin-Yang and Five Elements, the ancients believed that the mausoleum was a graveyard, and the Ming characters belonged to Yang. Add a horizontal line to the Ming character and it will become Yin Ming, so that it won't violate Feng Shui!
The third one is also the one I think is more practical.
I think it should be calligraphy characters, that is, from an aesthetic point of view, the characters are beautiful, the layout is symmetrical, and the expression languages in Chinese and English are different. China's writing is beautiful except for expressing meaning and paying attention to the balance between primary and secondary. There are many precedents in history for calligraphers to create and transform their own characters. In the process of writing, we found that this Japanese word has a left-right structure, which is called Riyueming. Small on the left, big on the right, it becomes ugly! So probably in the era of Wang Xizhi, a horizontal character was added to it and it became an eye. In the Tang and Song Dynasties, many calligraphers had such bright characters in their fonts, that is, adding a horizontal character to Japanese characters made them eyes.
Including the Republic of China, Dr. Sun Yat-sen also led officials to sweep graves in the Ming Tombs, expressing admiration for Ming Taizu's efforts to expel Tatars and restore China, so it was impossible to change the meaning of Ming characters at that time. It can't be said that there are no typos in the words written by Kangxi, and later generations have followed this pattern, so there are also typos written by Huangdi. We only need to open the Ming and Qing archives to see that there are still many batches. A typo? Therefore, if the emperor always writes horizontal lines by hand, no one dares to question and ask!