I 100% agree that people shouldn't stigmatize those with mental illnesses and that Tanner shouldn't be shamed for his struggles with depression. In fact, I think we pretty much all agree.
I suppose I could be missing the most offensive posts, or maybe the mods just delete them quickly, but I've never seen a post on here shaming Mangum for his depression. On the contrary, people rarely mention it and when he first spoke out there was a huge outpouring of support. The examples you've managed to come up with to support your point are not convincing at all (as others above are pointing out). What you call "code words" are run-of-the-mill criticisms used all the time against athletes who perform inconsistently or buckle under pressure or just can't find a groove. It's a huge stretch to suggest that when people say things like "something seems off with [Tanner]" they're shaming him for depression. A ridiculous stretch, imo.
I do think you mean well, but I think it's misguided. Tanner has talked about wanting to help eliminate the stigma associated with depression, but I'd seriously argue that in suggesting we treat him with kid gloves and avoid criticizing him in run-of-the-mill ways you're doing more to stigmatize him than any of the posts you're so offended by.