Ok, let me see if I can do this without confusing people too much. The reason that steel with a high carbon content causes problems is due to something called retained austinite. Austinite forms when you heat steel above around 1430°. This is a good thing at at this point. It allows carbon to dissolve into the iron in the steel which in turn is necessary to harden steel upon quenching. However, with steels that are above around 0.77% carbon this can cause the austinite not to convert to the hardened crystal of steel, known as martensite, and the austinite is retained, thus the name retained austinite. This will happen if the steel is heated too hot for too long. Now this really is not much of a problem until the carbon level gets above 0.85% carbon. A little retained austinite is not much of a problem but above 0.85% carbon a significant amount of retained austinite is formed. The problem with it is that retained austinite is not stable. It wants to form martensite and will over a period of time as stresses are applied to the steel. This martensite will be untempered and very hard and will increase the brittleness of the steel in higher concentrations.
1095 steel is around 0.95% carbon, note the last two numbers in the designation code, so it falls into the group of steels that can have a problem with retained austinite if heated too high for too long putting too much carbon into solution. After you get some experience under your belt and learn how to control the heat that you apply to your steel as you heat treat it's a good knife steel that a lot of makers, custom and commercial, use. To begin with, many recommed to beginners that they avoid such steels to start with.
If you are lost with the terminology or are unfamiliar with heat treating I suggest that you go the the metallurgy and heat treating section of this board and read the subjects within the sticky at the top of the page, Heat Treating Tool Box. Better yet, print it out. It will be enough to get you started and allow you to understand better the discussions on these boards.
Doug