The most-discussed stocks on the Reddit subforum WallStreetBets were mostly advancing in pre-market trading on Monday morning. IBM (NYSE: IBM) was among the notable movers, with shares indicated to open higher ahead of the regular session. Virgin Galactic (NASDAQ: SPCE) was also set to open higher, posting a pre-market gain of 36.42%. IBM shares were indicating a pre-market advance of 12.71%, placing the technology giant among the top gainers in…