Report? Report how? You mean because of MTL? You can’t. They dont care. Neither MD nor any other provider.
And its not that we "own" anything, you're missing the point. There are unspoken agreements thats 99% of scanlators stick to when it comes to uploading to a series which is already being worked, if there weren't, then it would just be utter chaos. If we bring a series on from scratch, build up a fan base then someone comes in and releases a part chapter a day before we can because of MTL and the fans (who will usually pretty much just read the first version released) will then stop reading our own.
You clearly don't scanlate otherwise you would understand how demoralising that is after the staff give up so much of their own free time.
Apart from anything else, combining when they're not released that was goes against MangaDexs ToS.
Firstly,yes,you can report someone,more so if they jumped multiple chapters,just gotta pray the mods actually get it done.
Secondly,it is already utter chaos,since folks are already posting whatever they feel like it,MTL or not,and it's only the readers shouting at them that occurs.
Considering that is the case,the so called "agreement"(which isn't even a Mangadex ruling)doesn't work,doesn't apply to anyone,and means that yes,you can just keep going if some chump shows up with their own version.
Third,readers are not blind,if a chump shows up with work less in quality then the other person,who hasn't gone AWOL,they'll stop reading it,come to the comment section,and shout at the dummy,said dummy would also not have the full chapter since the full chapter didn't come out.
In fact,this .1 and .2 system is more vulnerable to the very thing you're mentioning,since they can just upload the half themselves,and by your own statement,would cause you stop immediately since there would be no point.
Where as a full chapter of yours can't be beaten by a half chapter of theirs,that's not a demoralising situation,that's vindication that you're doing better then the other fella.
And finally,if you're talking agreements,that old outdated suggestion,it's not even a hard ruling,is actively ignored because it clearly flawed,a scanlator is the first to clearly see with no issue where the improper break lies.
This is a growing thing on Mangadex that is long overdue,why settle for a lower quality result that is more vulnerable to the thing you're afraid of when you can get something far better that can't be beat by anyone except another serious scanlator?,you're already on top of the latest releases,it would take extreme deliberate effort to scanlate both halves just to knock you out.
Additionally,just post your own anyway,they can't muscle you into stopping.
