Pictures take up way more space than text, it may give the warning it exceeds 10K characters but it isn’t meaning just text, you are bumping up against a size limit.  DM or IM clients are not meant for pictures or attachments.  Use the forum post or private email.

Agree with @ShawnBerk  here. Images take up many more characters. If you’re copying from word, that also comes with hidden characters.

I’d encourage you to have these conversations publicly, in a forum post, so that the entire community can benefit from the knowledge.