Idunno, the web browser has been discontinued for 3 years now. It also seems that bolt.co and Instagram's Bolt are much more similar to each other (apps dedicated to person→person communication) than Bolt the browser is to either of them, so the risk of confusion is much smaller.

Trademark is about preventing confusion, not owning words. A browser is very different from an app voice/text app.

My point was that the two Bolts barely compete with each other. One is for voice calls, the other is for quick picture sharing. I can't imagine many scenarios where you could use them interchangeably.

Fortunately, Bolt browser no longer exists and names, especially four letter common words, can't be reserved forever.

Technically they can. I could register whatever sequence of letters I want provided they can act as a unique identifier for me, and are not in themselves descriptive. If I register 'Bolt' for dog-walking services this is not descriptive and provided I pay my renewal fees I can protect the word forever, and take action against those whose use of it confuses users (for example 'Bolt' for dog food) or takes unfair advantage of the reputation in my mark.

The presence of a word in a dictionary/its length has no bearing on its registrability as a trade mark.

>provided I pay my renewal fees

That's my point. There's a maximum lifespan; the life of the company. Since Bolt browser no longer exists, I doubt they would renew the trademark.

I think the difference here is that the Bolt web browser was discontinued in 2011 (according to the Wikipedia article you linked), whereas the OPs "Bolt" voice/SMS service is very much an active project.

It's also hard to sympathize over confusion around a 4 letter word that's ALREADY a word.