After reading the responses coming from the creator of this suggestion. I get your point that new comers would join the server using damage indicator since they think that "oh jartex has damage indicator on minigames, so i dont need to turn off mine because i feel more comfortable with mine and im used to it being this way" even after they read the rule, a lot of them might still be thinking that it's allowed to use ONLY on minigames since damage indicator itself is built in minigames already so of course, there is a chance that they ignore the rule thinking that the rule is only applied for other gamemodes BUT Mini games, or they would be like "the rule section must be outdated because it claims that damage indicator isn't allowed GLOBALLY but I see it in minigames" but little that they don't know, jartex just meant that the modification is disallowed but that doesn't mean that jartex cant add their own one in a gamemode. It's just a confusion overall and innocent players might get banned this way due to new comers in the mini game section reporting cheaters while having their own damage indicator on and then get banned for it.
You're also right about new comers using damage indicator due to them thinking that it's not cheating and that it's not something big of a deal especially with damage indicator itself being built in minigames, it would make them think even more that it's allowed. As for them reading the rules, I talked about that above.
I also get your point that the only way someone would be caught using damage indicator is by getting SSed by a staff member and for that to happen, staff members should at least get a console alert of the player or be suspicious of them. So due to screenshare being the only way to catch damage indicator users, having damage indicator ALLOWED in minigames wouldn't be a problem because if they got SSed in minigames, they would be safe from getting banned from damage indicator, but if they got ssed in factions, they would be banned for using damage indicator because they're in the gamemode that damage indicator is disallowed.
But also, let's not forget that they will have to restart their MC for them to disable damage indicator every time they wanna switch to a gamemode after playing minigames. The reason why they have to restart MC is because, they can't have the damage indicator modification active in their minecraft game even tho they turned it "off" from the settings since staff members would never know if it was off or on. The modification should be removed completely while being in minecraft and for that, they will have to restart which could be annoying to players and that could make lazy players use damage indicator anyways which could create more damage indicator users.
Due to that being said, I think it's best that jartex network adds a MOTD that pops up in your screen every time someone joins the mini game gamemode saying "Jartex network built a damage indicator specifically made for mini games, so please avoid the use of damage indicator modification to prevent yourself from getting banned".
With that MOTD added, it would clear people from using it and remove the idea from their head about the use of damage indicator modification. That would also give an idea to new comers "oh, this network is strict about the use of damage indicator modification which probably means that it isn't allowed in other gamemodes"
This is the best way to deal with this situation, but of course if this suggestion gets accepted, it wouldn't be a problem too, but in my opinion, i think that it's best to add the MOTD.