I've been busy spinning my wheels and updating my video collection. I
discovered mkvtoolnix which is frankly awesome in that instead of
having to re-encode video for any mp4 with different options (audio,
subtitles), it allows me to extract and rearrange/include/exclude
tracks and put them into a new mkv file. I've written a helper script,
as you do, to expedite this. Of course now I'm being OCD
converting/extracting text captions and including them to reduce
filesizes. It "only" chops off a few MB (usually by removing foreign
language subtitles which I almost never use) per file, but considering
I have thousands of files, that's no small gain overall, although
given the effort I'm putting in, it may be a decent loss. At least I'm
keeping busy.

Anyway, to the title of this: I've recently been noticing more
artifacts and imperfections in my larger video encodings. Maybe it's
because I'm about 40 cm away from an HD monitor. Maybe it's because
I'm looking more and more at the direct MKV rips which usually have
twice the bitrate if not 20x or more. I don't know. What I do know is
that this phenomenon is not unprecedented: visual media on computers
are generally getting higher resolution and better picture quality, at
the expense of disk space and/or bandwidth, and previous "good"
resolutions look bad in comparison. I may not be the first to use the
term, but I call it HD spoilage, because it retroactively degrades
what used to be perfectly viable visual media. Indeed, even 720 isn't
regarded as "HD" by Youtube anymore. It's a shame. What I think is
even sillier is that bitrate, IMO, has much more to do with picture
quality than a width measurement.