Hey now! The tags stripping & links munching little helpers (let's call them Muncher and Stripper and not mind how wrong that sounds) are ferocious. I bred them that way. If you receive a nasty validation error or half your comment vanishes, something has triggered them, and they answer with full aggression, not 'micro' ones. Try and reformulate your text to appease them (for instance, beware of copy/pasting from Word or another web page). Use the preview to confirm you pass by Muncher and Stripper unmolested (now that didn't sound any better)
Stripper (oh dear, oh dear) will put a ✂ in place of anything that looks like a link—and he has about half the subtlety of a bombing raid over Dresden. (but makes for it with twice the hostility) Do.use.the.preview, even if you don't think you've inserted a link, for he may disagree and he's not open to negotiation.