Threads are a software concept dating back to at least 1967, and “software” is such a broad industry that I wouldn’t expect such a generic term to be able to apply to it in its entirety. Given that their (the plaintiff’s, not Meta’s) specific niche is messaging, where “thread” is another generic term (e.g., a “thread of discussion”) it seems doubly problematic as a trademark.

That all said, this lawsuit is in the UK, and they don’t even have attorneys over there (they have “barristers” and “solicitors”) and I have no clue if the same trademark standards apply.

In the US, another barrier would be the target audience. Threads by Meta is a B2C social media app; Threads by the Thread Company is a B2B corporate search index for internal messaging. Trademark dilution isn’t relevant - Threads wasn’t a famous brand before - and trademark infringement is based on the likelihood of customer confusion. Is it likely that a business professional - the sort of person who would be purchasing the B2C service - would confuse it with the social media app? I don’t think so, but that’s up to the legal system to decide.