Nothing about it is "legal." Copyright infringement is illegal.

If someone is no stranger to allegations of copyright infringement, it means he gets accused of copyright infringement a lot.

Copyright infringement is primarily a civil offense however there are options to prosecute criminally in the case of "willful and deliberate" acts of infringement.

Ignorance of the existence of copyright is not a viable defense to infringement. If an author is convicted of copyright infringement the publisher can be held liable for contributory infringement if it can be shown that they had knowledge of the infringement prior to publication. If, by a preponderance of the evidence, infringement can be shown then yes a damages award to the copyright holder can be granted.

no

"Copyright in fragment" is a common misspelling of "copyright infringement," which is the violation of copyright.