Sorry 'bout the confusion nvoigt. This is one of the quirks with our close vote system.
- People voted to close with a custom reason
- The custom reason gets listed as a comment (not in the close reason)
- The close reason defaults to 'off-topic'
Though it may not have been obvious, gnat's comment was actually a custom close reason he entered:
This question appears to be off-topic because it is about regulations or agreements that are company-specific and don't have universally applicable answers.
The comment is automatically generated whenever someone uses a custom close reason. Whenever someone else agrees with that reason, an upvote is automatically added. Currently it is at +5, which means people seemed to agree with the reason listed.
Unfortunately, with the write-in reasons, the banner that ends up getting put on the question explaining the close reason is quite vague. This is just the way it works after the close vote changes in 2013.
While I don't agree with the reason that was picked, I don't think it is on-topic because it is asking for people's opinion on a phenomenon that you haven't actually shown exists or is a widespread problem (your evidence is anecdotal and based on not getting a few jobs in a row). If you can show that there is a real problem here (with German employers not wanting to hire part-time developers), then adding that information to the question would improve it.
But while you're improving that part, you can go a step further. Rather than asking why they do it (which won't help you if you want a part-time development job), why not ask how to find the part-time jobs that are out there, or alternatively how to negotiate with an employer to hire you part-time for a full-time position, or something that will solve your problem (of not being able to get a part-time developer role)?
Hope that helps.