Having not found this thread earlier, I also reported this issue here:
Please note that it is NOT limited to just journalctl as reported here, but to EVERY command using more for its output, e.g. systemctl and many others. Even though I am aware of this issue, it happens quite often that I simply forget (or just don’t notice that more is used for output) and close the Terminal without first terminating the command first, and end up with a discharged battery a few hours later.
Even worse, it is not limited to just “more”. Other commands are also left running this way, e.g. top. It’s just that they don’t eat 100% CPU but e.g. the top process eats some 0.5 - 1% (or at least SO FAR I haven’t seen it going higher than that). But they also stay there and eat power and take CPU time and memory.
P.S. One more note: it doesn’t take being root, it also affects commands launched as defaultuser, e.g. the aforementioned systemctl.