Is this a bug or a feature? If I name a node anything starting with 2M, it turns that node into a voltage source that is 2mV

Nobody can help without details. What exactly are you trying to do? I have tested and a node can be named 2M<whatever> and works just fine. If you are using it as a number consider that for spice 2M = 2milli = 0.002 If you want Mega you need to use 2MEG As a general rule I suggest using for node names identifiers starting with an alphabetic character. a node named 2MCLK will work in spice but will definitely not work in Verilog or VHDL, as these languages prohibit using identifier starting with a number. for example in Verilog: