"I've never heard of it.."
Thanks for getting on here quick sharp to let us know. Looking forward to a fabulously informed and reasoned comment now. (Pipe down with the laughter at the back there - I know this is The Reg.)
"I like to think I'm reasonably up to date with all the latest fads"
You might want to revise your assesment of your skills on that front then. (Dunning-Kruger and all that)
"Still it is Java, you only have to wait 10 minutes and a new framework, API or dev enviroment will be along"
You missed the bit about Jenkins having been a thing for approaching a decade, and a thing under a different name for significantly longer? Sure there is plenty of stuff that has been around longer, but equally it is no new kid on the block.
And whilst it is written in Java, it can be used with a wide range of technologies, hence it being a *popular tool.
"Also someone who had colleagues constantly ringing him up with what were apparently quite obvious bugs in his checked in code..."
As already mentioned, I suspect there is at least a smidge of humble, self deprecation going on there, often a preciously short commodity in this industry.
"doesn't exactly strike me as the sort of coder who should be trusted to write something like this"
And yet Jenkins has been a thing for approaching a decade, a thing under a different name for significantly longer, and an indespensible tool for a lot of companies and orgs.
Other than them odds and ends, a cracking comment! Right on the money.
P.S. I am not a Java Dev.
* Popular is not necessarily the right word, as I, like the original commenter very much have a love/hate relationship with Jenkins, largely for the reasons they cited.