Yeah not recommended but I have seen it done many times.
I have seen an 8 way with another 8 way work fine. There is a lot you can get away with believe it or not.
Generally you want the following
2 way/2 way
4 way/2 way
8 way/2 way
Ok most of time
4 way/4 way
8 way/4 way
Try to avoid
8 way/8 way
If your using a Dswm13 LNB, you can generally get away stacking splitters as it requires 2 8way splitters to get all 13 tuners.
Generally where we see excess splitters is in a dish network conversion with a duo tuner receiver where the Tv2 feeds are being replaced with clients or other receivers.