I must admit that I haven't really come across that issue, mainly because I rarely if ever have a detection in a scan, other than when testing.
If you hover over a field that is concatenated, like this if you hover over the field does it not show all of the field ?
It may have more to do with the side window, have you tried to resize the window (as this window on my XP system is resizeable) ?
As an avast user like yourself - I have just done a test of some samples and I can expand the column width, unfortunately I can't replicate the issue.