Right, so we've already talk extensively about this in PM's and chat so I figured I would toss in my two cents here for you. Though I'll probably sound like I'm repeating myself.
Favoritism: I'm not fond of it, not on any level. If a mod is showing it intentionally or unintentionally they need to be informed about it as well as be told to cut it out. It can get nasty. Very, very nasty very quickly. Prioritization is different of course, major plot developments for PC's and such yeah they are more important obviously. So do I think its BS that this happened to you? Petch yeah, as a player you do have a right to be irritated by something like this if its continuous.
On the subject of grades being smaller than the effort put in, let me go on my own little tangent/example. I'm sure others can relate to this, you put in an absurd amount of time and effort into a thread and go into extreme detail in a thread. Then when the thread is graded the results are underwhelming. Maybe the Grader or ST was inexperienced, who knows, however you as a player should never feel intimidated to PM someone about this grade and ask why this occurred and what was their logic for such low rewards. That's why most grading posts have it written to PM them if you have questions about the grade after all.
Deus Ex Machina: Again, I can understand your frustration here and you've made it vocal to me that you considered it unfair. Sometimes however things play out a certain way, though it would seem rather like considering you were the one to award the item you should probably be consulted on matters like that. Honestly to do something like that on a single player, don't care who it is, kind of seems a bit like favoritism in and of itself. Say Jill over there is pious and faithful to their deity, shows it in every post and its a major part of whom her character is. Seems more likely God X would be more likely to take interest in them. Now you take Bob who is faithful to a certain degree, but not exactly committed to the whole thing or has their loyalties split to another god or two. Seems less likely honestly for a god to swoop down on high, just in my opinion.
Though, I guess it would also depend on how closely marked they are to that god. I mean, a priest seems more likely to gain the attention of a deity than a singularly marked person. Just looking as I see it. The above probably sounds rambling, hope it makes sense.
Power Level stuff: Ahhh... this is always such a lovely topic to see floating around. I used to indulge in this a bit, but at the end of the day its true such things are just mere speculation until it actually happens IC. Its an annoyance and I tend to steer clear of them now days. And yeah, of course masters and L3 marked are going to be powerful, they spent blood sweat and tears getting to that level. Not much to say on that particular subject, but yes, it can get annoying.
Conclusion: I don't think less of you or think you are being ungrateful. Radiant, you are one of the most active ST's on the site, you do right by your players and rarely if ever do I hear an ill word leveled your way. As a threading partner you are always punctual and polite, you try your hardest to make threads interesting and organic. If you have been dealing with such issues for so long a vent is necessary really. This is also your scrap so you can post what you want so long as it breaks no rules, which it does not. You are just possessed of concerns any player would in your position. I think you are brave to post something like this and well within your rights to do so.