If by Hud message you mean the one that goes in the centre of the screen I disagree regardless of if your refering to everyone else paying attention or the guy who is camping.
From the point of view of everyone else:Once the beacon sound starts going everyone who is intereste will hear it and look to see who the camper is on the chat line. If they can't hear it then they aren't close enough to take advantage of it anyway, and if they don't care then by slaping it in the middle of their screen you are making the camper even more of an anoyance than they were, which isn't the goal.
From the point of view of the camper:A big circle has just started to appear around them with a strange beeping noise, if they don't notice that then they arn't going to notice a message. Even if they don't know it's an anti-camp feature they are going to look to the chat line to try and work out what is going on as that usually holds some clue as to why a punishment is happening.
If you really want to get the attention of the camper though slap off a little health ever few seconds, slap sound included. There are only 2 things better at getting someones attention than removing some of their health. Those are remove all of their health or remove them from the game as a whole.
I've been running a non-sourcemod plugin that does this for the last 3 months and people pay attention to the chat line when you have the beacon and the sound to alert them to the camp offence.
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