Invalid html error on forum post

I get errors even if paste as plain text. Trying to link posts as a list (with or without bullets) is just a nightmare of errors.

This was a month ago dude...you guys are actually useless.

Hi arrrps​,

It looks like you were copy pasting rich-text content from another area to here. One way to avoid encountering this error is to use the "paste as plain text" feature in your browers.
That should make sure that any embedded html tags are removed and the post will go through as planned.