Speakers Corner

Speakers Corner is a good reissue house; Pallas is a good pressing plant. I doubt any plant would say they use mold release compound in their production since the pvc compound, as supplied, contains various things, including thermal stabilizers and material that helps ease removal from the stampers.
I'm with sbank- though largely buying old, used records, I clean any new ones too. 
CZ, I'm gonna send you a PM. 

Washline- if you go back and read my post, you'll see that I mentioned the fact that the so-called mold release is already in the pellets of PVC compound that are used to make the records. So, the notion that Pallas says they "don't use" mold release compound does not really address whether there are mold release agents, or other ingredients  in the vinyl compound itself that make it easier for a record to be removed from a stamper. There are a number of threads on this. I contributed to a couple, so I'd have to find them and give you links. 
I think the whole "mold release" thing is exaggerated, but it is very hard to get to the bottom of this- I did a fair amount of research on older vinyl compounds and found several papers published by the AES and some information in patents that described what goes into PVC for records. The formulations are often proprietary, so it's hard to pin down exactly what is in a given product, and presumably, a label or plant could order something that is different, from a different supplier, or with a different make up, than another record plant. (I don't know if you remember the whole thing about "Clarity" vinyl toward the end of Classic Records' production, but Mike Hobson claimed that eliminating the carbon black--used for antistatic purposes--improved the sound because it had electro-magnetic properties that interfered with the performance of the cartridge). 

As to cleaning, it seems to be a subject that everyone has a different view of- if your Speakers Corner copies play cleanly out of the sleeve, enjoy them. You might also investigate some of the original pressings that they remastered for their catalog. Although some are expensive, others aren't and if you are interested in what the differences in different masterings, tape sources and the like contribute to the end result, sonically, it is actually a fun process to compare pressings. 

Wash- it’s all part and parcel of the compound. With modern plants, as I understand it, the pellets are melted and extruded into nuggets/biscuits and that is what gets put onto the press. It’s not like the mold release is a liquid blob inside the nugget, it is all mixed together with various other materials that all perform different functions. I’m not a chemist or materials scientist, so the best I can do is tell you what I can glean from the old papers or patents- issues like "flow," stability, surface noise, evenness of heat application, discoloration- I can point you to some of the papers- some are only available through the AES by paid download or subscription to their library. One scientist was at RCA, and had written extensively on what was necessary to make a "modern" LP circa the ’70s. That wonderful JVC formulation used in the old MoFi’s was originally developed for Quad LPs.
There are clearly some sonic differences I would attribute to the vinyl used, but couldn’t tell you what role the constituent elements played. And no, as far as I know, none of this stuff would (or should) get removed by cleaning. The biggest issue I can think of-- which isn’t all that common, but occurs- is a chemical interaction between certain plastics and the record- for example, PVC outer record sleeves, which have plasticizers in them to make them soft. Those plasticizers will leach (through the cardboard jacket, the inner sleeve and onto the record itself) and in some cases, create a haze on the record that you can see and will affect sonics. I suspect it is also exacerbated by heat, i.e. storing the records in an attic. Cleaning won’t get rid of that- but that’s a chemical reaction- it’s like the off-gassing of the stuff in car dashboards that makes your windshield hazy.