When you comment in other people's journals, or reply to a comment they have made in your journal, do you try to use an icon that matches the fandoms/interests that you have in common; something that just appeals to you at the time, irrelevant or not as to whether the other person shares that interest; or the post's subject matter? Or, of course, a combination of all/some of these?
I believe that I do a combination. I usually try to match our 'likes'. That is, if I'm posting to the LJ of a Pros friend (who doesn't share my MFU, NCIS or DS likes), then most of the time I use a Pros icon, especially if the subject matter is about Pros. However, if I don't know the person to whom I'm commenting, i.e. they've posted a comment in respect of one of my stories, etc. then I tend to use an icon that ties in with the story/fandom.
Just an idle thought to while away a moment or two.