I would consider all of those positives on a resume.
Participation in user groups (in a leadership position, not just as a member), and teaching, both suggest interpersonal skills. I know some computer people who are talented, but...
[Choose any or all from the following list]
have terrible personal hygiene
can't carry on a conversation
can't work as part of a team
will not take direction
can't work on assignments they don't enjoy
won't document their code
take every opportunity to complain about policies they don't happen to agree with
alienate people who need their help
only want to learn new tools, no interest in producing any code
etc.
It's great if you can keep the entire source code for Linux in your head, but unfortunately a job requires actual production.
So if someone had a leadership position in a user group (believe me, it ain't hard to get one) that tells me they can work with others. They can organize and delegate. They probably have an interest in helping other people. Someone who was a member (but not in a position of responsibility) of a user group wouldn't count for very much on a resume, but it's a great way to network with other people. For that reason alone it's a worthwhile thing to do.
And writing articles would demonstrate excellent written communication skills which is another plus.
The person would obviously still need the technical skills and experience for the job, but any of those three attributes you mentioned would probably separate someone from the rest of the bunch.