A visual mark would be nice, agreed. I haven't tried it, but I wonder if you could approximate it with the bookmarking feature that less(1) does have. It wouldn't be visible, but it would scroll to a consistent mark.

I usually use tail when I need to do some ad-hoc log following.

Having to set bookmarks and remember them is a PITA I can usually do without. If I'm looking at "normal" log output, it's usually set up in a nice aggregator somewhere, where I can easily exclude noise and otherwise uninteresting output.