Any abnormality in a programmed system can be classified as a bug. I'm not wrong.
I think that's a bit too broad to be useful. I understand the temptation to view things that way, though.
It's tricky to come up with a good definition of what a bug is, but I think the legendary
Jargon File is difficult to improve on (taken from version 4.4.7):
bug noun: An unwanted and unintended property of a program or piece of hardware, esp. one that causes it to malfunction. [...]
I like this definition because it connects two important ideas (unwanted vs. unintended) with an "and" instead of a softer connective like "and/or" or just "or"; from your point of view (and probably most other people's, too) not being able to merit a post from an ignored board is
unwanted, but because you didn't write the code you can't also know if it is
unintended.
Only theymos can say whether this is a real bug or just a known limitation (I'm guessing it's the latter).