Download and use the plugin StatusSpec, which can be found here: http://www.teamfortress.tv/17560/statusspec
It has a function that enables highlighted killfeed for players even on an stv. First you'll need to enter the following command: statusspec_localplayer_enabled 1
This will enable the feature.
You next have to specify which player you would like the killfeed highlighted for. Unfortunately, the most convenient command to do this, statusspec_localplayer_set_current_target, has been broken for a while and doesn't look like it will be fixed anytime soon.
Fortunately, an alternative exists. You can still use statusspec_localplayer_player just fine.
In order to use this command you need to enter the following into console: statusspec_localplayer_player x,
where "x" is the player index number. Basically, if there are 12 people in the server, each player will have a number assigned to them ranging from 1-13 I believe (13 because it counts the free camera located inside the map as a player for some reason). It will take some trial and error to find the correct number corresponding to the player you want the killfeed highlighted for but it shouldn't take too long at all.
So for example, if the player you wanted to highlight the killfeed for had an index number of "5" you'd first enable the localplayer feature, i.e. enter statusspec_localplayer_enabled 1 into console. Then you'd enter statusspec_localplayer_player 5 into console. The killfeed for that player should now be highlighted.
I was really frustrated for ages thinking that the plugin was broken but was so happy when Beater told me about this alternative method. So yeah, I hope this helps!