XF 2.3 Where is the width of the poster are controlled??

[The Chip Spa]

ie.

The user name looks wonky if too long

 

[MentaL]

.message-cell.message-cell--user {
    flex: 0 0 240px;
}

 

[The Chip Spa]

.message-cell.message-cell--user {
    flex: 0 0 240px;
}

where is that located?

 

[The Chip Spa]

 

[The Chip Spa]

Found it here Thanks