Emiri-san said:
Yeah don't use notes to label characters.
I don't agree with this as a strict policy. For the vast majority of images, maybe, but there are those occasional few posts with hordes of characters in them where I think it can be useful. The post #219801 that Demuwu remarked on is one but we also have a few examples from kantai_collection, and I recall seeing others in the past.

It's not always practical to find information on characters online, especially if the character in question is obscure enough and from Japanese or other foreign language media which means whatever sources do exist about it are most likely also in that language. In these cases having our own on-site information helps. And even if that research is a practical option, it might simply be quicker to check "note guides" like in the above-linked images.

There are also a few other rare cases in which I think it's helpfully informative to note-label characters:
-Images wherein characters are depicted that, for whatever reason, we've decided against tagging on Konachan. Arthur's work on labeling individual types of KanColle Equipment Fairies is an example of this.
-Images wherein the characters depicted would for some reason be abnormally challenging to differentiate from each other and/or the rest of the image (such as post #268594 ); this is not only helpful for viewers but also for parties interested in tagging to cross-reference with the tags and keep track of who has and hasn't been identified.
-Images wherein characters are depicted at such small sizes as to impair casual discernment of which characters they are.

Also, notes don't interfere with much of anything else on the site if they're created, aside from visually on the image they're applied to, but that can be remedied easily enough with the hide notes function on each post. Of course, if it were more common to have to deal with that while browsing images, some users might consider it obnoxious. But if it's just in those few images loaded with characters, I think it's not a problem.