Multi Line Column + Enhance Rich Text Formatting being lost

Hello, 

say I have a multi line column + rich text enhanced in a SP list. I have a few paragraph with a bold header at the top of each paragraph.

When another user goes in and edits the cell, the bolding goes away. and sometimes the paragraph collapse into 1 big paragraph with out my previous spacing.

Whats going on here? What can i do to prevent this?