I can see some one is attempting to high-wake and I can take action.
If I could see someone is mlogging I could take steps to ensure they don't escape unmolested.
A notification would definitely make sense as we also get notified of a FSD charge.
The difference between these two things is that jumping one's ship to another system is a CMDR action performed via in-game equipment in a wholly in-setting context, but menu logging is a player action performed via their game client.
I don't feel the game needs to announce player actions in an in-character context. This would set a negative precedent that may make it more difficult to implement better mechanisms in the future...not that I really expect better mechanisms to come, but an extra fifteen seconds of wasted time every other encounter is a small price to pay for not closing that door, IMO.
It is the not knowing and assuming that you are just there to kill them; that causes the issues.
It's as well within the bounds of the game as the other activities you mention.
The only issue is that the game provides a way to spontaneously opt-out of content (essentially any form of danger that can take longer than 15 seconds to resolve) that one has already opted into.
Any suggestion for dealing with combat logging has to cope with the situation where two players are instanced together, then they lose the connection with each other but both still communicate with FD.
The game has been able to relay clients that could not directly connect before. Even used to be a setting to force it in AppConfig.xml...not entirely sure if it still works or not.
Same could be if you have a low ping with someone, again, some indicator (beyond the obvious rubberbanding that will be happening anyway), but at least explain why shots that appear to hit don't appear to be doing damage.
Rubberbanding can certainly occur when the connection or client load gets really bad, but latency in and of itself won't cause a shot that appears to hit to miss because the latency compensation scheme used each client's own perspective takes precedence when inflicting damage, even if the result looks absurd (a high ping can mean two CMDRs in a duel can each be shooting the other up the tailpipe from their own perspectives, because the game says both perspectives are correct).
If ping is high enough to be a major issue through latency compensation, then matchmaking should simply refuse to pair such clients with each other.