Under ideal lighting conditions, there will be very little difference between images shot with or without a high quality, multi-coated filter. Especially if other reasonable precautions are taken, such as using a good fitted lens hood to protect the filter from oblique light. (Good fitted lens hoods and lens caps both do a far better job "protecting" lenses, too.)
HOWEVER, under more extreme lighting even an excellent filter can cause issues. For example, directly shooting a sunset or sunrise with the bright sun within the image, you should remove any and all filters.
But possibly more to the point, with today's cameras and lenses the UV filter serves virtually no purpose at all. Digital imaging sees very little to no benefit from filtering out UV light (the way film did, because it tended to be overly sensitive to UV, causing a bluish cast to scenes). A thin piece of glass provides very little physical protection, too. In fact, a broken filter might even do damage that could have been avoided. And modern lenses are a lot tougher than most people think.
The problem is, sales people are only too happy to sell you things you don't really need or should be really low priority. There's also a misunderstanding of UV filters (and similar Sky, 81A warming, etc.) that a lot of experienced photographers used back in the days of film... That was because of film's over-sensitivity to UV light, generally NOT to physically "protect" the lenses, as many have assumed (even though the glass in vintage lenses and the coatings used on them were a lot more susceptible to damage).
Plus, people who use UV filters "all the time" today generally don't make comparisons. They often screw them on their lenses rather permanently and never shoot without... let alone look at images with and without filters side-by-side. A perfect example was the earlier forum post you mention.... where someone was concerned about the lack of contrast and saturation they were seeing with one of their lenses. He or she put a filter on it and never really made any comparisons, until noticing that another recently purchased lens without a filter seemed to render images with so much more "pop". Even then, it didn't occur to him (or her) that the filter might be the culprit. But when someone finally asked about it and the lens was tested without the filter... "Boom!" Problem solved! As much difference as we saw in the image examples provided in that thread, I suspect the filter in question might have been lower quality, uncoated or single coated. But even "the best" are going to cost a little bit of IQ all the time.... and can cost considerably more in extreme situations.
I've seen that sort of thing time after time.... For example, a lot of users of the Canon EF 100-400mm L lens (original push-pull version) were stunned to learn how much sharper their lens was after they removed the "protection filter" from it, that they though it needed and installed from new. That particular lens simply doesn't "play well" with filters.... even the highest quality, multi-coated onse cause it to "go soft". (I don't know if the 100-400mm Mark II version does the same.... I've never fitted mine with any filter, in the two years I've been using it. I'll have to do a test some day.)
It doesn't help that users are very quick to defend their purchase and use of a UV filter by citing supposed "lenses saved", with no real proof that the filter did anything other than break. To truly prove it one way or another would mean buying multiple copies of many different types of lenses, fitting half of them with filters and half without, then putting them aall through a series of rigourous, destructive tests to see if on average there's any improvement in survival likely related to using the filter as "protection". No one has ever undertaken such an extensive test and likely no one ever will.
But at least
some testing has been done. It might not be exahustively definitive, but can at least help. Watch and judge for yourself:
https://www.youtube.com/watch?v=P0CLPTd6Bds(Note that in at least one case a sheet of plain paper held up better than a filter did!)
All that said... Yeah, I've got high quality, multi-coated UV filters available for use on most of my lenses. They're stored separately in my camera bag and are among my least-used accessories. I only get em out and install them when shooting in a situation where they actually might serve a purpose (i.e., a sandstorm.... or at the beach... or, occasionally, a scene with bluish haze where I'm not using a C-Pol for one reason or another). Because they spend probably 99.98% of the time unused and stowed in my bag, UV filters were among my lowest priority purchases. In comparison, quality circular polarizing filters were a MUCH higher priority.... serving many more purposes and on my lenses a lot more often! I probably use a C-Pol for 10 or 15% of shots overall.... maybe 50 or 60% of scenic shots, in particular. They're also useful for automotive, other products and even portraiture at times.
In the end, I've spent a lot on high quality lenses and cameras to make the best images possible. Those lenses don't NEED protection and the LAST thing I'm going to do is mindlessly stick anything between my lenses' optics and the subject I'm trying to capture in an image, as best I can.
P.S. Your filter is B+W brand (not B&W). German-made and the XS-Pro series is their very top of the line.... They use excellent Schott glass, 16-layer "Nano" multi-coatings that are a bit more scratch resistant and easier to clean than some, in a slim brass frame that's less likely to get stuck than aluminum. It is probably either an "010M" (which is what they call their "UV") or a "Clear" protective only filter. This high quality filter will minimize risk of image degradation in all but the most severe lighting conditions. If it's a UV, it also might occasionally serve to slightly reduce a bluish haze in a scene (Clear protective won't).