Does the angels' saying amen to a prayer for others apply to prayer said aloud or silently, and must a person tell someone they slandered about the false story when apologising?

Summary

The angels say amen to a prayer made for a fellow Muslim whether it is recited aloud or silently, as it falls under the general meaning of prayer. In prostration, a prayer in Arabic is permitted, while a prayer in another language is kept in the heart. For the wrong of slander, whether to inform the victim depends on the situation, weighing harm against benefit, together with seeking forgiveness, repenting, replacing the slander with good words and defending the victim's honour.

Written in our own words from the original fatwa — check the source before acting on it.