I reviewed code changes for hardfork 13 and assisted the core devs in finding issues and iterating on the design of the new mining algorithm included in v0.13.0.
I provided a suggestion for how to fix the unvoting bug. Thanks goes to @abit for taking my suggested fix and actually making the pull request for the patched code, which has now been merged to develop.
I found a problem with the new hot algorithm and recommended a solution to fix it. My recommend fix has now been implemented in the develop branch.
I have also been working on some ideas related to curation. Particularly, I've been thinking about a design to allow those with excess voting power to sell their rshares in a market. Then curators would have the option to buy the best offers of rshares in the market using their own SD up to a specified price or amount at the same time that they vote on a post/comment in order to boost their voting influence beyond what their current SP and voting power gives them normally. This allows curators who strongly believe they have found a highly undervalued post to get a larger share of the curation rewards than they could with their SP alone by paying some SD out of their pocket. The price they pay is determined by the market: how badly excess rshares is in demand by curators versus how desperate SP holders are to sell off their excess rshares that they aren't putting to good use so that they can make some extra money. Because the excess rshares will disappear in a relatively short time period if it isn't put to use (either used by the SP holder to vote, or sold in this rshares/SD market), the market price for the excess rshares could potentially be quite affordable for curators since it is better for an SP holder to at least get something (even if it is not much) rather than nothing.
After some discussion with @complexring, I am also beginning to think through the design of a curation delegation feature. The rshares market discussed in the previous paragraph is good for curators who have some extra liquid capital that they are willing to spend to get a temporary boost in their voting influence and correspondingly larger curation rewards (but they don't want to spend their liquid capital to buy more SP, which while it would give the curator a boost in voting influence, it would be a longer-term boost at the cost of requiring significantly larger amounts of their liquid capital to be spent to buy the SP, which may not be worth it for the curator). However, there is also demand by some curators who want to have more voting influence and correspondingly get larger curation rewards but would rather pay for it not through their capital but with their time. In other words, if someone is willing to supply the capital (really the rshares made possible from the large SP holdings) then those curators will spend their time finding good posts and voting on the capital supplier's behalf with only the request that the curator gets some agreed upon cut of the curation rewards they generate. This is where a curation delegation feature could come in handy. An auction market is not good for this type of arrangement because this arrangement requires the capital provider to trust the curators they hire to some degree (and to oversee their curation to make sure they are doing a decent job) since the capital providers payment is contingent upon the curators they contract with doing a good job in curation. Instead the curation delegation feature should allow the capital provider to specify some limited number of curators (assuming the curators also agree) that are allowed to tap into capital provider's voting power, and for each curator, the capital provider would specify percentage of the curation rewards earned that goes to them as well as the rate limit on how quickly the curator can consume the voting power.
For now, I will only be working on both the rshares market and the curation delegate feature at the conceptual design stage and not spend too much of my time on it, unless Steemit core devs express a desire to actually see any of these features included into Steem.