Asking questions will never make you the “black sheep”, rather it indicates curiosity and a willingness to learn.
A very good definition of “tainted kernel” was found here.
When the kernel is tainted, it means that **it is in a state that is not supported by the community** . Most kernel developers will ignore bug reports involving tainted kernels, and community members may ask that you correct the tainting condition before they can proceed with diagnosing problems related to the kernel. In addition, some debugging functionality and API calls may be disabled when the kernel is tainted.
**In most cases involving proprietary drivers, you can safely ignore the taint condition** , but some scenarios which cause the kernel to become tainted may be indicative of serious system problems.
The feature is intended to identify conditions which may make it difficult to properly troubleshoot a kernel problem. For example, the loading of a proprietary module can make kernel debug output unreliable because kernel developers don't have access to the module's source code and therefore cannot determine what the module may have done to the kernel. Likewise, if the kernel had previously experienced an error condition or if a serious hardware error had occurred, the debug information generated by the kernel may not be reliable.
**The kernel may become tainted for any of several reasons** , including (but not limited to) the following:
* The use of a proprietary (or non-GPL-compatible) kernel module—this is the most common cause of tainted kernels and usually results from loading proprietary NVIDIA or AMD video drivers
* The use of *staging* drivers, which are part of the kernel source code but are not fully tested
* The use of *out-of-tree* modules that are not included with the Linux kernel source code
* Forcible loading or unloading of a kernel module (such as forcibly inserting a module not built for the current version of the kernel)
* The use of an SMP (multiprocessor) kernel on certain unsupported uniprocessor CPUs, primarily older AMD Athlon processors
* Overriding of the [ACPI](https://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface) DSDT, sometimes needed to correct for power-management bugs (see [here](https://wiki.archlinux.org/index.php/DSDT) for details)
* Certain critical error conditions, such as [machine check exceptions](https://en.wikipedia.org/wiki/Machine-check_exception) and [kernel oopses](https://en.wikipedia.org/wiki/Linux_kernel_oops)
* Certain serious bugs in the system firmware (BIOS, UEFI) which the kernel must work around
Each of these conditions is represented by a particular flag in the kernel. **Some Linux vendors, such as SUSE, [add additional taint flags](http://www.novell.com/support/kb/doc.php?id=3582750)** to indicate conditions such as loading a module that is not supported by the vendor.
More information is available in the [kernel documentation](https://www.kernel.org/doc/html/v4.10/admin-guide/tainted-kernels.html).