Signature visible on mobile

Check this link

https://www.blackhatworld.com/seo/wtb-100-homepage-links-tech-niche.1545731/
Many members signature links showing there on mobile itself. Is this a bug?

It's consistent for these members, I collected screenshots of them for a week or two.

One thing, though, is that these sigs look very similar to each other.

These aren't signatures. They are simply posting the same thing repeatedly in their posts and could be warned for doing so, however as the post you're signposting is in the want to buy section it's acceptable here as per the guidance. The best option would be to report these posts if you find them where the spam posting rule would apply.

You can always see someone's sig in their profile for example https://www.blackhatworld.com/members/awesomewebsites.238934/#about

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