Cavalary: While you're here, a few issues, which may be long-standing and may have already been mentioned, don't know that, but either way:
I'm not here, but MaGog notifies me whenever someone posts in this thread.
Cavalary: Even if you select not to include removed games, they, or at least some, are included. Noticed it again due to throwing off the (now further reduced after the Brazilian launch) count for [url=http://www.an-ovel.com/cgi-bin/magog.cgi?ver=751&scp=gdsp&dsp=ipgfsorc&flt=prp~0~pat~0.01~&opt=nsf]the flat-priced search[/url].
If we take your example, the scopes requested include Premium Editions and exclude Removed Games, among others. Now, the question is what should MaGog do with a game such as Fallout Classic, which is both premium and removed. The default, which you have used, is to include any game that meets at least one included scope, e.g. premium (this is called a "Greedy" algorithm). The opposite algorithm (called "Restrained") will exclude any game that meets at least one excluded scope, e.g. removed. You can choose which algorithm to use via the "Scope Algorithm" option. Just use "Restrained" (this will add an "r" to the opts= field in the URL) and all the removed games will disappear. For more on this, see the Version 6.4.4 entry on the ChangeGog page.
Cavalary: Not sure if exactly a bug, but sorting by price sorts by current price, not full. [url=http://www.an-ovel.com/cgi-bin/magog.cgi?ver=751&scp=gdsp&dsp=ipgfsorc&ord=p9&flt=tcs~oddworld~&opt=nsf]Example.[/url] With the option available below only applying to regional prices, if this is intentional maybe there could be two sorting options, full price and current price.
As you rightly state, the Show/Sort Current/Full option, as labelled, only refers to regional prices. The base price sorting is always based on full price. The reason is quite simple: as far as I remember, nobody ever asked for the current price sort. I'll get to adding it later this week (assuming I manage to tear myself away from Etherlords).
Cavalary: Also, why does removing the version parameter from the URL make it ignore scope restrictions (or at least that's what I noticed first)? That same flat-priced search with that removed also returns upcoming games for example. If it behaves differently according to it, shouldn't it default to most recent if missing?
The version field was added to the URL in version 1.3.2. Therefore, if it is missing, MaGog assumes the search was generated by a pre-1.3.2 GUI and acts accordingly (yes, there are still links on the forum from that time, and yes, they are still being clicked on, based on MaGog's logs). Since pre-1.3.2 MaGog had only three scopes: DLC (d), removed (r), and everything else (g), as soon as you have a "g" in your scope (i.e. "Regular Games"), you also get everything else (e.g. upcoming, season passes, in dev, demos).
Hint: Don't delete the version field.