Sina Corp. (NASDAQ:SINA) may have just announced another better-than-expected quarter, but the market still isn't quite ready to reward the Chinese Internet company for its efforts. After waffling between positive and negative territory early Wednesday, shares of Sina traded up a modest 1.5% as of 2:00 p.m.

On one hand, Sina's adjusted quarterly revenue climbed 14% year over year to $211 million, including a 13% increase in advertising revenue to $176.3 million. On the other hand, that translated to a 67% decrease in adjusted net income to $4 million and a 65% drop on a per-share basis to $0.06. Analysts, on average, were less optimistic on both fronts, with consensus estimates predicting lower second-quarter revenue of $200.8 million, and adjusted earnings of just $0.05 per share.

Way to go, Weibo
Sina's micro-blogging site, Weibo (NASDAQ:WB), exhibited relative strength, achieving adjusted earnings of $10.9 million, of $0.05 per share. That was well above analysts' expectations for earnings of $0.03 per share, and represents a huge improvement over its adjusted net loss of $5.1 million, or $0.03 per share, in the same year-ago period. 

Sina CEO Charles Chao added, "We are confident that with Weibo's firm execution in growing user base and engagement, capitalizing on the mobile strategy, and leveraging partnership with Alibaba to enable e-commerce Transactions, the powerful social media platform and cohesive ecosystem that we have built can better fulfill the needs of users, customers and merchants at various dimensions and can generate sustainable earnings and cash flows and create long-term value to our shareholders."

That said, investors aren't particularly encouraged that Weibo remains the primary driver of Sina's growth; Weibo's $28.3 million increase in advertising and marketing revenue more than offset Sina's $7.9 million decline in portal advertising sales. To be fair, adjusted non-advertising revenue climbed 21.3% year over year to $34.7 million, driven by a combination of Sina's new business initiatives and sales from Weibo's games and membership fees, and offset in part by declines in Weibo data license revenue.

A massive vote of confidence
"We are delighted that SINA has further implemented its vertical and mobile strategies," insisted Chao, "and launched a set of constructive corporate actions to better leverage SINA's brand equity, capture business opportunities, and give momentum to the capital market." For perspective on the latter, recall the Chinese stock market -- and, consequently, shares of Sina -- suffered tremendous volatility over the past two months. Chinese regulators took a number of steps in response intended to stabilize the market, including making additional financing available for margin lending, allocating billions of dollars to buying back Chinese stocks, and orchestrating a widespread halt to new IPOs and share issuances.

Chao also insisted Sina has "great confidence" in its long-term growth potential, noting its mobile efforts have yielded "robust growth in user traffic and improved monetization for the past quarters." 

And Chao is putting his money where his mouth is. In June, Sina stock soared after he agreed to make a massive $456 million cash investment in 11,000,000 newly issued shares of the company. Sina says the transaction is expected to complete "upon satisfaction of customary closing conditions," after which Chao's new shares will be subject to a contractual lockup period of six months.

In addition, Sina revealed since approving its $500 million repurchase plan in April of last year, it repurchased a total of 8.1 million shares for $311 million by the time the authorization expired on May 31, 2015. While those repurchases have failed to boost Sina's stock price, if anything, they've served to at least partially offset the impending dilutive impact of Chao's large investment.

Finally, during the subsequent conference call, Chao stated Sina is choosing not to revise its guidance for the full year due to "a lot of uncertainties going forward." Specifically, while Weibo has shown improvement, Sina is exercising caution given the current macroeconomic situation, as well as the ongoing challenge of leveraging mobile to offset declines in the PC portal side of the business. In March, Sina offered initial guidance for a wide full-year 2015 revenue range of $800 million to $900 million, the mid-point of which sits slightly above analysts' current average estimate of $841.6 million.

In the end, with those uncertainties in mind and as long as Weibo continues its outsized role in driving Sina's results, it's hard to blame the market for today's muted reaction to Sina's latest quarterly beat.

Steve Symington has no position in any stocks mentioned. The Motley Fool recommends Sina. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.