1
Get the video you want on mlb.com, and there will be a little box that says "Embed"
Click there should open a box with text like this:
<iframe src='http://m.mariners.mlb.com/shared/video/embed/embed.html?content_id=79308...' width='400' height='224' frameborder='0'>Your browser does not support iframes.</iframe>
Copy that.
Then "Disable rich-text" on your post or comment and paste that text in. Then "Enable rich-text" again.
Should give you this:
Add pithy line like "nice slo-mo of the rising heat at 0:17" and you should be set. Prior Klat platforms didn't work with "iframes" which is what all the mlb.com videos will give you for embedding.