Does reading tombstones cause forgetfulness?

Writing on graves is prohibited and disliked. Some فقهاء (jurists) have mentioned that reading what is written on graves leads to forgetfulness, as Ibn al-Jawzi said in "Al-Hathth ala Hifdh al-Ilm" (Incitement to Preserve Knowledge) that "reading the tablets of graves" is among the things that lead to forgetfulness. However, there is no Shar'i (Islamic legal) or customary evidence to support that reading this writing leads to forgetfulness.