A "coherent argument" means presenting ideas or reasons in a clear and logical way, so that others can understand and be convinced by them. Full definition
Surely no one who isn't a lawyer can actually stand up and make coherent arguments (advocacy) on a complex legal topic? (slaw.ca)
That is, if students work on logic puzzles, they get better at logic puzzles but not at other things, such as forming coherent arguments or winning debates. (scientificamerican.com)
Then, if you can make a more coherent argument, you're welcome to post comments. (deepclimate.org)