You can't directly change individual columns, but you can reduce the "Text" column. This is done in themes/default/elog.css. Search for "listtitle2" and change or remove the line "width:100%". This makes the text column narrower, leaving more space for the subject column.
I'm trying to expand the Subject column, when viewing in summary mode, and couldn't find any documentation for it. Is this possible and if so, how would I do it.
Thanks in advance for your help.