in my opinion, abstention is essentially a wasted vote/a way to split the vote. spending money to say you officially don't care about something is a funny concept to me. :D
it's also a way to ignore someone's poll. say, someone that isn't very well-liked in the community creates a poll... rather than having to give their poll actual thought, many could vote abstain, and it would be like a group shunning. i think some of the past polls and proposals have been sort of ridiculous, but we have to regard everyone's ideas with the same respect. "majority rule don't work in mental institutions...", but i don't think many of us are actually insane. true democracy might be observed here.
a new user creating a poll wouldn't know what to expect for "lowest valid voter participation"... i think that might be a bit unrealistic.
these are my ideas about your ideas. lol. and i do agree with you that more thought needs to be given to contingencies, etc, before changing the amount. for example, the developer compensation poll... if it had failed, the developers wouldn't have been paid at all. that's fairly ludicrous, and kinda sorta extortion. not wanting to see the developers get paid at all, and being against a pay increase - are 2 different things, but they were lumped together in this way.
I think the abstain option is a good idea because the alternative would be not voting. You could consider not voting as an abstain, but then again, do you really know if they read the proposal and decided they don't care about the outcome? or did they miss the poll in its entirety? If you don't have that abstain option, you really don't know.
If you set up rigid categories like I explained above, new users will probably be making casual polls which I don't think should require a minimum vote weight requirement, because casual polls shouldn't be actionable and only get a community opinion per se. New users who have a high balance in order to make the bigger polls, are obviously invested in gridcoin, and probably have/should have done their homework about what vote weight to select before making an important poll. Simply put, I don't think this will be much of an issue.
As for the recent developer compensation poll, I don't see this situation as the fault of this poll. If you add a clause like "if this poll does not pass, developers will continued to be paid $30/hr", then you're saying if it fails, part of the poll will be enacted anyway. Which makes my stomach feel weird to be honest. The problem is that the previous poll (the one that paid devs $30/hr initally) only stated it would be in effect for the next 6 months. What it should have stated was the $30/hr had no expiration, and we would have a poll every 6 months to review it.