Is it permissible to speak loudly in the mosque about worldly matters, and to clear one's throat in a way that disturbs those praying, and what are the consequences of that?

Mosques were built for the remembrance of Allah, prayer, reading the Quran, and disseminating knowledge. Those who sit in them should observe proper etiquette and avoid anything contrary to these purposes. There is no harm in a little worldly conversation and smiling. Indeed, the Companions used to converse with the Prophet (peace be upon him) in the mosque and laugh at incidental matters. However, excessive idle talk, gossip, and boisterous laughter are disliked. If those conversing are advised but defiantly persist in their transgression, this indicates their ignorance.