What about “Communal logmarks”? To logmark a line that isn’t already logmarked, click it’s time field. From now till someone or something unhighlights it, that line will be highlighted for you. And for everyone else. It’s a communal logmark. Anyone (or anything) can click again to unhighlight.
Original gist below, with couple minor edits.
I am very happy you’ve done what you’ve done. I say the prognosis just sharply improved for #perl6 summaries, my carpal tunnel pain, and your irclogger software!