What is the religious ruling on those who cause annoyance to worshippers in the Two Holy Mosques by choosing adjacent spots or sitting in front of them during crowded times, and are there clear pieces of advice and fatwas regarding this matter?

What some people do, stepping over people's necks and pushing to reach the front rows for prayer, is wrong and harms others, distracting them from their devotion in prayer. Abu Dawud narrated, and Al-Albani graded it good, from the Prophet, peace and blessings be upon him, that whoever attends Jumu'ah (Friday prayer) listening and silently, and does not step over a Muslim's neck, nor harms anyone, it will be an expiation for him until the following Jumu'ah, plus three more days. This hadith indicates that the reward is not in pushing and stepping over necks for those who are late, but rather in adhering to Islamic manners. Therefore, a Muslim should not harm others or push them to pray in the front rows.