You are right, these are opinions, as there aren't any statistics to base the recommendations on. The thing is, this phenomenon has only recently been recognized, and no one has done an official study to publish in any scientific journals yet. What you have are adverse effect reports, which are given to Bayer and shared among colleagues (on websites, during meetings, and through consultations). The reasoning behind the recommendation for subQ injection is that an injection site reaction happening at the surface is much easier to recognize early, easier to treat, and less likely to cause debilitating damage.

The original statement, "Most of the scaring from baytril is because it wasnt injected into the meat but under the skin," is just wrong. Scarring happens when the animal has a reaction to the drug -- whether in the subcutaneous tissues or the muscles -- leading to necrosis which (hopefully) heals eventually resulting in a scar. The point I'm trying to get across is that no matter where you inject the drug, or how perfect your technique is, you still are at risk of having a reaction.